diff --git a/lib/js/runtime.sx b/lib/js/runtime.sx
index 72bc49b3..cae5f94f 100644
--- a/lib/js/runtime.sx
+++ b/lib/js/runtime.sx
@@ -105,6 +105,125 @@
       ((= key "length") 0)
       (else :js-undefined))))
 
+(define
+  js-invoke-number-method
+  (fn
+    (recv key args)
+    (cond
+      ((= key "toString")
+        (let
+          ((radix (if (empty? args) 10 (nth args 0))))
+          (js-num-to-str-radix
+            recv
+            (if
+              (or (= radix nil) (js-undefined? radix))
+              10
+              (js-to-number radix)))))
+      ((= key "toFixed")
+        (js-number-to-fixed
+          recv
+          (if (empty? args) 0 (js-to-number (nth args 0)))))
+      ((= key "valueOf") recv)
+      ((= key "toLocaleString") (js-to-string recv))
+      ((= key "toPrecision") (js-to-string recv))
+      ((= key "toExponential") (js-to-string recv))
+      (else
+        (error
+          (str
+            "TypeError: "
+            (js-to-string key)
+            " is not a function (on number)"))))))
+
+(define
+  js-invoke-boolean-method
+  (fn
+    (recv key args)
+    (cond
+      ((= key "toString") (if recv "true" "false"))
+      ((= key "valueOf") recv)
+      (else
+        (error
+          (str
+            "TypeError: "
+            (js-to-string key)
+            " is not a function (on boolean)"))))))
+
+(define
+  js-num-to-str-radix
+  (fn
+    (n radix)
+    (cond
+      ((and (number? n) (not (= n n))) "NaN")
+      ((= n (/ 1 0)) "Infinity")
+      ((= n (/ -1 0)) "-Infinity")
+      ((or (= radix 10) (= radix nil) (js-undefined? radix))
+        (js-to-string n))
+      (else
+        (let
+          ((int-n (js-math-trunc n)))
+          (if
+            (< int-n 0)
+            (str "-" (js-num-to-str-radix-rec (- 0 int-n) radix ""))
+            (js-num-to-str-radix-rec int-n radix "")))))))
+
+(define
+  js-num-to-str-radix-rec
+  (fn
+    (n radix acc)
+    (if
+      (= n 0)
+      (if (= acc "") "0" acc)
+      (let
+        ((d (mod n radix)) (rest (js-math-trunc (/ n radix))))
+        (js-num-to-str-radix-rec rest radix (str (js-digit-char d) acc))))))
+
+(define
+  js-digit-char
+  (fn
+    (d)
+    (cond
+      ((< d 10) (js-to-string d))
+      (else (let ((offset (+ 97 (- d 10)))) (js-code-to-char offset))))))
+
+(define
+  js-number-to-fixed
+  (fn
+    (n digits)
+    (let
+      ((d (js-math-trunc digits)))
+      (if
+        (< d 1)
+        (js-to-string (js-math-round n))
+        (let
+          ((scale (js-pow-int 10 d)))
+          (let
+            ((scaled (js-math-round (* n scale))))
+            (let
+              ((int-part (js-math-trunc (/ scaled scale)))
+                (frac-part
+                  (- scaled (* (js-math-trunc (/ scaled scale)) scale))))
+              (let
+                ((frac-abs (if (< frac-part 0) (- 0 frac-part) frac-part)))
+                (str
+                  (js-to-string int-part)
+                  "."
+                  (js-pad-int-str (js-to-string (js-math-trunc frac-abs)) d))))))))))
+
+;; parse a decimal number from a trimmed non-empty string.
+;;   s      — source
+;;   i      — cursor
+;;   acc    — integer part so far (or total for decimals)
+;;   sign   — 1 or -1
+;;   frac?  — are we past the decimal point
+;;   fdiv   — divisor used to scale fraction digits (only if frac?)
+(define
+  js-pow-int
+  (fn (b e) (if (<= e 0) 1 (* b (js-pow-int b (- e 1))))))
+
+(define
+  js-pad-int-str
+  (fn (s n) (if (>= (len s) n) s (js-pad-int-str (str "0" s) n))))
+
 (define
   js-apply-fn
   (fn
@@ -136,6 +255,8 @@
             (nth args 5)))
         (else (apply callable args))))))
 
+;; ── String coercion (ToString) ────────────────────────────────────
+
 (define
   js-invoke-method
   (fn
@@ -144,6 +265,8 @@
       ((and (js-promise? recv) (js-promise-builtin-method? key))
         (js-invoke-promise-method recv key args))
       ((js-regex? recv) (js-regex-invoke-method recv key args))
+      ((number? recv) (js-invoke-number-method recv key args))
+      ((boolean? recv) (js-invoke-boolean-method recv key args))
       (else
         (let
           ((m (js-get-prop recv key)))
@@ -169,6 +292,9 @@
       (= name "valueOf")
       (= name "toLocaleString"))))
 
+;; ── Arithmetic (JS rules) ─────────────────────────────────────────
+
+;; JS `+`: if either operand is a string → string concat, else numeric.
 (define
   js-invoke-object-method
   (fn
@@ -194,13 +320,6 @@
 
 (define js-lower-case (fn (s) (js-case-loop s 0 "" false)))
 
-;; parse a decimal number from a trimmed non-empty string.
-;;   s      — source
-;;   i      — cursor
-;;   acc    — integer part so far (or total for decimals)
-;;   sign   — 1 or -1
-;;   frac?  — are we past the decimal point
-;;   fdiv   — divisor used to scale fraction digits (only if frac?)
 (define
   js-case-loop
   (fn
@@ -279,8 +398,6 @@
   js-invoke-method-dyn
   (fn (recv key args) (js-invoke-method recv key args)))
 
-;; ── String coercion (ToString) ────────────────────────────────────
-
 (define
   js-call-plain
   (fn
@@ -307,9 +424,7 @@
             ret
             obj))))))
 
-;; ── Arithmetic (JS rules) ─────────────────────────────────────────
-
-;; JS `+`: if either operand is a string → string concat, else numeric.
+;; Bitwise + logical-not
 (define
   js-instanceof
   (fn
@@ -338,6 +453,9 @@
             ((not (= (type-of p) "dict")) false)
             (else (js-instanceof-walk p proto))))))))
 
+;; ── Equality ──────────────────────────────────────────────────────
+
+;; Strict equality (===): no coercion; js-undefined matches js-undefined.
 (define
   js-in
   (fn
@@ -356,6 +474,9 @@
       ((dict-has? obj "__proto__") (js-in-walk (get obj "__proto__") skey))
       (else false))))
 
+;; Abstract equality (==): type coercion rules.
+;; Simplified: number↔string coerce both to number; null == undefined;
+;; everything else falls back to strict equality.
 (define
   Error
   (fn
@@ -392,6 +513,11 @@
           nil)
         this))))
 
+;; ── Relational comparisons ────────────────────────────────────────
+
+;; Abstract relational comparison from ES5.
+;; Numbers compare numerically; two strings compare lexicographically;
+;; mixed types coerce both to numbers.
 (define
   RangeError
   (fn
@@ -428,7 +554,6 @@
           nil)
         this))))
 
-;; Bitwise + logical-not
 (define
   ReferenceError
   (fn
@@ -459,18 +584,19 @@
         (= t "component")
         (and (= t "dict") (contains? (keys v) "__callable__"))))))
 
-;; ── Equality ──────────────────────────────────────────────────────
-
-;; Strict equality (===): no coercion; js-undefined matches js-undefined.
 (define __js_proto_table__ (dict))
 
 (define __js_next_id__ (dict))
 
-;; Abstract equality (==): type coercion rules.
-;; Simplified: number↔string coerce both to number; null == undefined;
-;; everything else falls back to strict equality.
 (dict-set! __js_next_id__ "n" 0)
 
+;; ── Property access ───────────────────────────────────────────────
+
+;; obj[key] or obj.key in JS. Handles:
+;;   • dicts keyed by string
+;;   • lists indexed by number (incl. .length)
+;;   • strings indexed by number (incl. .length)
+;; Returns js-undefined if the key is absent.
 (define
   js-get-ctor-proto
   (fn
@@ -482,11 +608,6 @@
         (else
           (let ((p (dict))) (begin (dict-set! __js_proto_table__ id p) p)))))))
 
-;; ── Relational comparisons ────────────────────────────────────────
-
-;; Abstract relational comparison from ES5.
-;; Numbers compare numerically; two strings compare lexicographically;
-;; mixed types coerce both to numbers.
 (define
   js-reset-ctor-proto!
   (fn
@@ -501,6 +622,7 @@
     (ctor proto)
     (let ((id (js-ctor-id ctor))) (dict-set! __js_proto_table__ id proto))))
 
+;; Setter — mutates the dict. Returns the new value (JS assignment yields rhs).
 (define
   js-ctor-id
   (fn
@@ -510,6 +632,10 @@
         (get ctor "__ctor_id__"))
       (else (inspect ctor)))))
 
+;; ── Short-circuit logical ops ─────────────────────────────────────
+
+;; `a && b` in JS: if a is truthy return b else return a. The thunk
+;; form defers evaluation of b — the transpiler passes (fn () b).
 (define
   js-typeof
   (fn
@@ -539,6 +665,9 @@
       ((= v "") false)
       (else true))))
 
+;; ── console.log ───────────────────────────────────────────────────
+
+;; Trivial bridge. `log-info` is available on OCaml; fall back to print.
 (define
   js-to-number
   (fn
@@ -556,15 +685,9 @@
   js-string-to-number
   (fn (s) (cond ((= s "") 0) (else (js-parse-num-safe s)))))
 
-;; ── Property access ───────────────────────────────────────────────
+;; ── Math object ───────────────────────────────────────────────────
 
-;; obj[key] or obj.key in JS. Handles:
-;;   • dicts keyed by string
-;;   • lists indexed by number (incl. .length)
-;;   • strings indexed by number (incl. .length)
-;; Returns js-undefined if the key is absent.
 (define js-parse-num-safe (fn (s) (cond (else (js-num-from-string s)))))
-
 (define
   js-num-from-string
   (fn
@@ -574,18 +697,10 @@
       (cond
         ((= trimmed "") 0)
         (else (js-parse-decimal trimmed 0 0 1 false 0))))))
-
 (define js-trim (fn (s) (js-trim-left (js-trim-right s))))
-
-;; Setter — mutates the dict. Returns the new value (JS assignment yields rhs).
 (define
   js-trim-left
   (fn (s) (let ((n (len s))) (js-trim-left-at s n 0))))
-
-;; ── Short-circuit logical ops ─────────────────────────────────────
-
-;; `a && b` in JS: if a is truthy return b else return a. The thunk
-;; form defers evaluation of b — the transpiler passes (fn () b).
 (define
   js-trim-left-at
   (fn
@@ -594,14 +709,9 @@
       ((>= i n) "")
       ((js-is-space? (char-at s i)) (js-trim-left-at s n (+ i 1)))
       (else (substr s i n)))))
-
 (define
   js-trim-right
   (fn (s) (let ((n (len s))) (js-trim-right-at s n))))
-
-;; ── console.log ───────────────────────────────────────────────────
-
-;; Trivial bridge. `log-info` is available on OCaml; fall back to print.
 (define
   js-trim-right-at
   (fn
@@ -610,13 +720,9 @@
       ((<= n 0) "")
       ((js-is-space? (char-at s (- n 1))) (js-trim-right-at s (- n 1)))
       (else (substr s 0 n)))))
-
 (define
   js-is-space?
   (fn (c) (or (= c " ") (= c "\t") (= c "\n") (= c "\r"))))
-
-;; ── Math object ───────────────────────────────────────────────────
-
 (define
   js-parse-decimal
   (fn
@@ -648,7 +754,8 @@
               sign
               false
               0)))
-        (else (* sign (if frac? (/ acc fdiv) acc)))))))
+        (else (* sign (if frac? (/ acc fdiv) acc)))))))   ; deterministic placeholder for tests
+
 (define
   js-is-digit?
   (fn
@@ -665,6 +772,11 @@
         (= c "7")
         (= c "8")
         (= c "9")))))
+
+;; The global object — lookup table for JS names that aren't in the
+;; SX env. Transpiled idents look up locally first; globals here are a
+;; fallback, but most slice programs reference `console`, `Math`,
+;; `undefined` as plain symbols, which we bind as defines above.
 (define
   js-digit-val
   (fn
@@ -681,6 +793,7 @@
       ((= c "8") 8)
       ((= c "9") 9)
       (else 0))))
+
 (define
   js-to-string
   (fn
@@ -693,9 +806,11 @@
       ((= (type-of v) "string") v)
       ((= (type-of v) "number") (js-number-to-string v))
       (else (str v)))))
+
 (define
   js-template-concat
   (fn (&rest parts) (js-template-concat-loop parts 0 "")))
+
 (define
   js-template-concat-loop
   (fn
@@ -707,7 +822,9 @@
         parts
         (+ i 1)
         (str acc (js-to-string (nth parts i)))))))
+
 (define js-number-to-string (fn (n) (str n)))
+
 (define
   js-add
   (fn
@@ -716,14 +833,11 @@
       ((or (= (type-of a) "string") (= (type-of b) "string"))
         (str (js-to-string a) (js-to-string b)))
       (else (+ (js-to-number a) (js-to-number b))))))
-(define js-sub (fn (a b) (- (js-to-number a) (js-to-number b))))   ; deterministic placeholder for tests
+
+(define js-sub (fn (a b) (- (js-to-number a) (js-to-number b))))
 
 (define js-mul (fn (a b) (* (js-to-number a) (js-to-number b))))
 
-;; The global object — lookup table for JS names that aren't in the
-;; SX env. Transpiled idents look up locally first; globals here are a
-;; fallback, but most slice programs reference `console`, `Math`,
-;; `undefined` as plain symbols, which we bind as defines above.
 (define js-div (fn (a b) (/ (js-to-number a) (js-to-number b))))
 
 (define js-mod (fn (a b) (mod (js-to-number a) (js-to-number b))))
diff --git a/lib/js/test.sh b/lib/js/test.sh
index b6512405..771a67f5 100755
--- a/lib/js/test.sh
+++ b/lib/js/test.sh
@@ -1169,6 +1169,28 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 3405)
 (eval "(js-eval \"var arr2 = [1,2]; Array.prototype.push.call(arr2, 10, 20); arr2.length\")")
 
+;; ── Phase 11.nummethod: .toString(), .toFixed() on numbers ───
+(epoch 3600)
+(eval "(js-eval \"(5).toString()\")")
+(epoch 3601)
+(eval "(js-eval \"(16).toString(16)\")")
+(epoch 3602)
+(eval "(js-eval \"(10).toString(2)\")")
+(epoch 3603)
+(eval "(js-eval \"(3.14).toFixed(1)\")")
+(epoch 3604)
+(eval "(js-eval \"(3.14).toFixed(2)\")")
+(epoch 3605)
+(eval "(js-eval \"(0).toFixed(3)\")")
+(epoch 3606)
+(eval "(js-eval \"(7).valueOf()\")")
+(epoch 3607)
+(eval "(js-eval \"true.toString()\")")
+(epoch 3608)
+(eval "(js-eval \"false.toString()\")")
+(epoch 3609)
+(eval "(js-eval \"(true).valueOf()\")")
+
 ;; ── Phase 11.arrlike: Array.prototype.* on {length, 0:..., 1:...} ──
 (epoch 3500)
 (eval "(js-eval \"var a = {length: 3, 0: 41, 1: 42, 2: 43}; Array.prototype.slice.call(a).length\")")
@@ -1819,6 +1841,18 @@ check 3403 "fn.call this-binding"          '42'
 check 3404 "fn.apply arg-unpack"           '7'
 check 3405 "Array.prototype.push.call arr" '4'
 
+# ── Phase 11.nummethod: number/boolean methods ────────────────
+check 3600 "(5).toString()"                '"5"'
+check 3601 "(16).toString(16)"             '"10"'
+check 3602 "(10).toString(2)"              '"1010"'
+check 3603 "(3.14).toFixed(1)"             '"3.1"'
+check 3604 "(3.14).toFixed(2)"             '"3.14"'
+check 3605 "(0).toFixed(3)"                '"0.000"'
+check 3606 "(7).valueOf()"                 '7'
+check 3607 "true.toString()"               '"true"'
+check 3608 "false.toString()"              '"false"'
+check 3609 "(true).valueOf()"              'true'
+
 # ── Phase 11.arrlike: array-like receivers on Array.prototype ─
 check 3500 "slice.call arrLike length"     '3'
 check 3501 "slice.call arrLike join"       '"41,42,43"'