#include <iostream>
using namespace std;

unsigned long long n;

int main()
{
	cin >> n;

	for ( unsigned long long i = 2; i * i < n; i++ ) {
		if ( n % i == 0 ) {
			cout << "NO" << endl;
			return 0;
		}
	}

	cout << "YES" << endl;

	return 0;
}