Question

Given two different prime numbers p and q, find the number of different natural divisors of the number. p^m*q^n

Answer 1

The formula for the number of divisors (d) is
  d = (m+1)(n+1)
where this number includes the values 1 and p^m*q^n

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This can be generalized to more or fewer prime factors. Add 1 to each of the exponents and form the product of those values.