What made you believe that the program hang? One thing is for sure that, the program will run for quite a while before it finally figures out that 429496731 is a prime.

You don't need to test every integer that is smaller than the input number. You only need to try up to its sqrt(). (You can further improve this, but what I suggested here is an easy fix to the situation with the least amount of effort.)

Peter (Guo) Pei

In reply to Re: is_a_prime test? by PeterPeiGuo
in thread is_a_prime test? by Anonymous Monk

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