include <bits/stdc++.h>

using namespace std; int a; bool kt(int b) { if(b<2) return false; for(int i=2;i*i<=b;i++) { if(b%i==0) return false;

}
return true;

} int main() { cin>>a;

if(kt(a)) cout<<"YES";
else cout<<"NO";

return 0;

}