diff -r 7d3da112e2c1 -r eecf6077ec4e emul/mini/src/main/resources/org/apidesign/vm4brwsr/emul/lang/java_lang_Number.js
--- a/emul/mini/src/main/resources/org/apidesign/vm4brwsr/emul/lang/java_lang_Number.js	Tue Feb 05 16:32:14 2013 +0100
+++ b/emul/mini/src/main/resources/org/apidesign/vm4brwsr/emul/lang/java_lang_Number.js	Tue Feb 05 16:40:01 2013 +0100
@@ -113,15 +113,6 @@
     return hi.next32(low);
 };
 
-Number.prototype.div64 = function(x) {
-    var low = Math.floor(this.toFP() / x.toFP()); // TODO: not exact enough
-    if (low > __m32) {
-        var hi = Math.floor(low / (__m32+1)) | 0;
-        return hi.next32(low % (__m32+1));
-    }
-    return low;
-};
-
 Number.prototype.and64 = function(x) {
     var low = this & x;
     low += (low < 0) ? (__m32+1) : 0;
@@ -213,3 +204,313 @@
     var ret = hi.next32(low);
     return ret.add64(1);
 };
+
+function __initDivMod(numberPrototype) {
+    function __Int64(hi32, lo32) {
+        this.hi32 = hi32 | 0;
+        this.lo32 = lo32 | 0;
+
+        this.get32 = function(bitIndex) {
+            var v0;
+            var v1;
+            bitIndex += 32;
+            var selector = bitIndex >>> 5;
+            switch (selector) {
+                case 0:
+                    v0 = 0;
+                    v1 = this.lo32;
+                    break;
+                case 1:
+                    v0 = this.lo32;
+                    v1 = this.hi32;
+                    break;
+                case 2:
+                    v0 = this.hi32;
+                    v1 = 0;
+                    break
+                default:
+                    return 0;
+            }
+
+            var shift = bitIndex & 31;
+            if (shift === 0) {
+                return v0;
+            }
+
+            return (v1 << (32 - shift)) | (v0 >>> shift);
+        }
+
+        this.get16 = function(bitIndex) {
+            return this.get32(bitIndex) & 0xffff;
+        }
+
+        this.set16 = function(bitIndex, value) {
+            bitIndex += 32;
+            var shift = bitIndex & 15;
+            var svalue = (value & 0xffff) << shift; 
+            var smask = 0xffff << shift;
+            var selector = bitIndex >>> 4;
+            switch (selector) {
+                case 0:
+                    break;
+                case 1:
+                    this.lo32 = (this.lo32 & ~(smask >>> 16))
+                                    | (svalue >>> 16);
+                    break;
+                case 2:
+                    this.lo32 = (this.lo32 & ~smask) | svalue;
+                    break;
+                case 3:
+                    this.lo32 = (this.lo32 & ~(smask << 16))
+                                    | (svalue << 16);
+                    this.hi32 = (this.hi32 & ~(smask >>> 16))
+                                    | (svalue >>> 16);
+                    break;
+                case 4:
+                    this.hi32 = (this.hi32 & ~smask) | svalue;
+                    break;
+                case 5:
+                    this.hi32 = (this.hi32 & ~(smask << 16))
+                                    | (svalue << 16);
+                    break;
+            }
+        }
+
+        this.getDigit = function(index, shift) {
+            return this.get16((index << 4) - shift);
+        }
+
+        this.getTwoDigits = function(index, shift) {
+            return this.get32(((index - 1) << 4) - shift);
+        }
+
+        this.setDigit = function(index, shift, value) {
+            this.set16((index << 4) - shift, value);
+        }
+
+        this.countSignificantDigits = function() {
+            var sd;
+            var remaining;
+
+            if (this.hi32 === 0) {
+                if (this.lo32 === 0) {
+                    return 0;
+                }
+
+                sd = 2;
+                remaining = this.lo32;
+            } else {
+                sd = 4;
+                remaining = this.hi32;
+            }
+
+            if (remaining < 0) {
+                return sd;
+            }
+
+            return (remaining < 65536) ? sd - 1 : sd;
+        }
+        
+        this.toNumber = function() {
+            var lo32 = this.lo32;
+            if (lo32 < 0) {
+                lo32 += 0x100000000;
+            }
+
+            return this.hi32.next32(lo32);
+        }
+    }
+
+    function __countLeadingZeroes16(number) {
+        var nlz = 0;
+
+        if (number < 256) {
+            nlz += 8;
+            number <<= 8;
+        }
+
+        if (number < 4096) {
+            nlz += 4;
+            number <<= 4;
+        }
+
+        if (number < 16384) {
+            nlz += 2;
+            number <<= 2;
+        }
+
+        return (number < 32768) ? nlz + 1 : nlz;
+    }
+    
+    // q = u / v; r = u - q * v;
+    // v != 0
+    function __div64(q, r, u, v) {
+        var m = u.countSignificantDigits();
+        var n = v.countSignificantDigits();
+
+        q.hi32 = q.lo32 = 0;
+
+        if (n === 1) {
+            // v has single digit
+            var vd = v.getDigit(0, 0);
+            var carry = 0;
+            for (var i = m - 1; i >= 0; --i) {
+                var ui = (carry << 16) | u.getDigit(i, 0);
+                if (ui < 0) {
+                    ui += 0x100000000;
+                }
+                var qi = (ui / vd) | 0;
+                q.setDigit(i, 0, qi);
+                carry = ui - qi * vd;
+            }
+
+            r.hi32 = 0;
+            r.lo32 = carry;
+            return;
+        }
+
+        r.hi32 = u.hi32;  
+        r.lo32 = u.lo32;
+
+        if (m < n) {
+            return;
+        }
+
+        // Normalize
+        var nrm = __countLeadingZeroes16(v.getDigit(n - 1, 0));
+
+        var vd1 = v.getDigit(n - 1, nrm);                
+        var vd0 = v.getDigit(n - 2, nrm);
+        for (var j = m - n; j >= 0; --j) {
+            // Calculate qj estimate
+            var ud21 = r.getTwoDigits(j + n, nrm);
+            var ud2 = ud21 >>> 16;
+            if (ud21 < 0) {
+                ud21 += 0x100000000;
+            }
+
+            var qest = (ud2 === vd1) ? 0xFFFF : ((ud21 / vd1) | 0);
+            var rest = ud21 - qest * vd1;
+
+            // 0 <= (qest - qj) <= 2
+
+            // Refine qj estimate
+            var ud0 = r.getDigit(j + n - 2, nrm);
+            while ((qest * vd0) > ((rest * 0x10000) + ud0)) {
+                --qest;
+                rest += vd1;
+            }
+
+            // 0 <= (qest - qj) <= 1
+            
+            // Multiply and subtract
+            var carry = 0;
+            for (var i = 0; i < n; ++i) {
+                var vi = qest * v.getDigit(i, nrm);
+                var ui = r.getDigit(i + j, nrm) - carry - (vi & 0xffff);
+                r.setDigit(i + j, nrm, ui);
+                carry = (vi >>> 16) - (ui >> 16);
+            }
+            var uj = ud2 - carry;
+
+            if (uj < 0) {
+                // qest - qj = 1
+
+                // Add back
+                --qest;
+                var carry = 0;
+                for (var i = 0; i < n; ++i) {
+                    var ui = r.getDigit(i + j, nrm) + v.getDigit(i, nrm)
+                                 + carry;
+                    r.setDigit(i + j, nrm, ui);
+                    carry = ui >> 16;
+                }
+                uj += carry;
+            }
+
+            q.setDigit(j, 0, qest);
+            r.setDigit(j + n, nrm, uj);
+        }
+    }
+    
+    numberPrototype.div64 = function(x) {
+        var negateResult = false;
+        var u, v;
+        
+        if ((this.high32() & 0x80000000) != 0) {
+            u = this.neg64();
+            negateResult = !negateResult;
+        } else {
+            u = this;        
+        }
+
+        if ((x.high32() & 0x80000000) != 0) {
+            v = x.neg64();
+            negateResult = !negateResult;
+        } else {
+            v = x;
+        }
+
+        if ((v === 0) && (v.high32() === 0)) {
+            // TODO: throw
+        }
+
+        if (u.high32() === 0) {
+            if (v.high32() === 0) {
+                var result = (u / v) | 0;
+                return negateResult ? result.neg64() : result; 
+            }
+
+            return 0;
+        }
+
+        var u64 = new __Int64(u.high32(), u);
+        var v64 = new __Int64(v.high32(), v);
+        var q64 = new __Int64(0, 0);
+        var r64 = new __Int64(0, 0);
+
+        __div64(q64, r64, u64, v64);
+
+        var result = q64.toNumber();
+        return negateResult ? result.neg64() : result; 
+    }
+
+    numberPrototype.mod64 = function(x) {
+        var negateResult = false;
+        var u, v;
+        
+        if ((this.high32() & 0x80000000) != 0) {
+            u = this.neg64();
+            negateResult = !negateResult;
+        } else {
+            u = this;        
+        }
+
+        if ((x.high32() & 0x80000000) != 0) {
+            v = x.neg64();
+        } else {
+            v = x;
+        }
+
+        if ((v === 0) && (v.high32() === 0)) {
+            // TODO: throw
+        }
+
+        if (u.high32() === 0) {
+            var result = (v.high32() === 0) ? (u % v) : u;
+            return negateResult ? result.neg64() : result; 
+        }
+
+        var u64 = new __Int64(u.high32(), u);
+        var v64 = new __Int64(v.high32(), v);
+        var q64 = new __Int64(0, 0);
+        var r64 = new __Int64(0, 0);
+
+        __div64(q64, r64, u64, v64);
+
+        var result = r64.toNumber();
+        return negateResult ? result.neg64() : result; 
+    }
+};
+
+__initDivMod(Number.prototype);