#include<bits/stdc++.h>
using namespace std;
#define ll long long

bool is_prime(ll n) {
    if (n <= 1) {
        return false;
    }
    if (n <= 3) {
        return true;
    }
    if (n % 2 == 0 || n % 3 == 0) {
        return false;
    }
    ll i = 5;
    while (i * i <= n) {
        if (n % i == 0 || n % (i + 2) == 0) {
            return false;
        }
        i += 6;
    }
    return true;
}

signed main() {
    ll n;
    cin >> n;

    if (is_prime(n)) {
        cout << "YES" << "\n";
    } else {
        cout << "NO" << "\n";
    }