Power inputs at python

I have an excercise for my programming class where I want to make a python program that uses Fermat's Test to test if a given number is prime or not. I have written my program but I have never used python before so I have the following problem. When I give as input e.g. 2**4 the program prints an error instead of calculating if 16 is a prime or not. What can I do so it will do what I want it to do?