package yukicoder;

import java.util.Scanner;

public class No3023 {
    public static void main(String[] args) {
        int n = new Scanner(System.in).nextInt();
        int rootN = (int)Math.pow(n, 0.5);
        boolean res = false;

        for(int i = 2; i <= rootN; i++) {
            if(n % i == 0) {
                res = true;
                break;
            }
        }

        if(n == 1) {
            System.out.println("NO");
            return;
        }
        System.out.println(res ? "NO" : "YES");
    }
}