Question

A program in C that checks if a number is a prime number.

I got these conditions so far:

if (num == 2 || num%2 != 0 && num > 1)
printf("%d is a prime number.\n", num);
else
printf("%d is not a prime number.\n", num);

But I don't know what to do with numbers like 9, 15, 21...

Answer 1

Or am I going to need a loop here?

Answer 2

you should go for a loop