Divisor counting

Count the number of divisors of a number given its prime factors in the form:

If a number n look like this:

n = a^p * b^q * c^r * d^s * e^t * f^u ... ,

where a,b, c and so on are its prime factors

then the number of divisors of n = (p+1)*(q+1)*(r+1)*...

This is because we can choose any number of a's from 0 to p, which gives us (p+1) choices, and so on.

http://mathforum.org/library/drmath/view/55741.html