Are You A Prime Number

Question

I\'ve been interested in the problem of finding a better prime number recognizer for years. I realize this is a huge area of academic research and study - my interest in this i

Answer 1

Even numbers(except 2) cannot be prime numbers. So, once we know that the number is not even, we can just check if odd numbers are it's factors.

for (i = 3; i <= ceiling; i += 2) {
        if (input % i == 0) {
            factorFound = 1;
            break;
        } 
    }