It seems that many people would like to have this, so it's now a sequel to this challenge!
Definition: a prime power is a natural number that can be expressed in the form pn where p is a prime and n is a natural number.
Task: Given a prime power pn > 1, return the power n.
input output 9 2 16 4 343 3 2687 1 59049 10
Scoring: This is code-golf. Shortest answer in bytes wins.