#include <iostream>

using namespace std;

bool prime_number(unsigned long long n)
{
    if(n == 0 || n == 1)
        return false;
    for(unsigned long long i = 2; i * i <= n; ++i)
        if(n % i == 0)
            return false;
    return true;
}

int main()
{
    cout << "Please enter a number: ";
    unsigned long long number;
    cin >> number;

    if(prime_number(number))
        cout << "YES\n";
    else
        cout << "NO\n";
    return 0;
}