Numero Primo O No Primo

Leer un numero y determinar si es primo o no primo

#include<iostream>

using namespace std;

int main()

{

         int num,aux,div;

         div=0;

         cout<<"ingrese numero"<<endl;

         cout<<endl;

         cin>>num;

         aux=num;

         cout<<endl;

         while (num>0)

         {

               if (aux%num==0)

               {

                     div=div+1;

               }

               num-=1;

         }

         if (div>2)

         {

         cout<<"el numero no es primo"<<endl;

         cout<<endl;

         }

         else

         {

         cout<<"el numero es primo"<<endl;

               cout<<endl;

         }

         system ("pause");

         return 0;

}