Finding prime numbers with C

primes.c

#include <stdio.h>

int main( int argc, char *argv[]) {
    
    if (argc < 2)
        printf("must supply argument - range");
    
    int devisors = 0, num, devisor, largest, range = atoi(argv[1]);

    for (num = 7; num < range; num += 2) {
        devisors = 2;

        if (num % 5 == 0 || num % 3 == 0)
            continue;

        for (devisor = 2; devisor < num; devisor++) {
            if (num % devisor == 0) {
                devisors++;

                if (devisors > 2)
                    break;
                
            }    
        }

        printf("num = %d | devisors = %d\n", num, devisors);
        
        if (devisors == 2) 
            printf("%d is prime\n", num);
    }


   return 0;
}