#include<iostream> // cin\cout\endl #include<cstdio> //scanf()\printf() #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; int main(){ int n; cin>>n; for(int i=2;i*i<=n;i++){ if(n%i==0) cout<<"NO"<<endl;return 0; } cout<<"YES"<<endl; return 0; }