int main()
{
    unsigned long long x = 600851475143 ;
    unsigned long long  z =     600851475143 ;
    unsigned long long  y =1;
bool isPrime = true;
    for (z=x; z> 0; z--)
    {
        if (x % z == 0)
        {
            printf("z = %lu", z);
            for (y = 2 ; y < z; y++)
            {
				isPrime = true;
                if ((z%y == 0) && (isPrime))
                {
                   isPrime = false;
					break;
				}
            }
            if (isPrime)
            {
                printf("Final prime = %lu", z);
            } 

        }
    }
    return 0;
}

Line 3: error: integer constant is too large for 'long' type
compilation terminated due to -Wfatal-errors.