The number prototype object itself is a Number object (has [[Class]] = "Number") whose value is +0.
The [[Prototype]] property is the standard built-in Object prototype object (15.2.4).
The prototype methods for Number are not generic. The object context needs to be a Number or an object with [[Class]] = "Number". Otherwise a TypeError is thrown.
Number Number.prototype.constructor
string Number.prototype.toString([radix:uint])
string Number.prototype.toLocaleString()
number Number.prototype.valueOf()
string Number.prototype.toFixed(fractionDigits:uint)
string Number.prototype.toExponential(fractionDigits:uint)
string Number.prototype.toPrecision(precision:uint)