L

#include <iostream>
#include <set>
#include <map>
#include <vector>
#include <algorithm>

using namespace std;

#define li long long

bool isprime(long long n) {
	for (long long i = 2; i * i <= n; i++) {
		if (n % i == 0) {
			return 0;
		}
	}
	return 1;
}

int main() {
	int i;
	cin >> i;
	if (isprime(i)) {
		cout << "YES";
	}
	else {
		cout << "NO";
	}


	return 0;
}