Math is a toolkit with certain math specific methods.
Math.[[Prototype]] is the standard Object prototype.
Math.[[Class]] = "Math"
Math has no [[Construct]] property so you can't use it in a new expression (but you can inherit from it ;)).
Math has no [[Call]] property, as such it's not possible to use it as a function.
The specification notes that "the Number value for x" has the meaning as defined in 8.5.