Function for primes

[aitía]

I wish to write a function that determines if a number is prime (1) or not (0). The only rule I know to apply is to write them in the form of 6n + 1.

int    is_prime(int nb)
{
    int    i;

    i = 2;
    while (i < nb)
    {
        i++;
    }
    if (nb % nb == 0) // Prime
        return (1);
    return (0);
}