Why is Math.prototype undefined?

I must be missing something here, because Math.prototype is undefined for me. Why is this? I tried to do something like this:

Math.prototype.randomRange = function(from, to){
    return Math.floor(Math.random() * (to - from + 1) + from);
}

But instead had to do something like this:

Math.randomRange = function(from, to){
    return Math.floor(Math.random() * (to - from + 1) + from);
}

That doesn't feel right, though. Is it just me or should I be doing this another way? I apologize if this is a silly or duplicate question, but I couldn't find anything by searching (exactly two questions turn up when I search SO for "Math.prototype", which is kind of weird).