Perfect

#include <stdio.h>

int main(void)
{
    for (unsigned int p = 2; p <= 23; p++) {
        unsigned long long m = (1ULL << p) - 1;

        int prime = 1;

        for (unsigned long long i = 2; i * i <= m; i++) {
            if (m % i == 0) {
                prime = 0;
                break;
            }
        }

        if (prime)
            printf("%llu\n", (1ULL << (p - 1)) * m);
    }
}