import java.util.Scanner;
public class Prime{
public static void main(String[] args) {
int i;
int j=0;
Scanner sc=new Scanner(System.in);
int k=sc.nextInt();
for(i=2;i<k;i++){
if(k%i==0)
j++;
}
if(j==0){
System.out.println("YES");
}else{
System.out.println("NO");
}
sc.close();
}
}