c++ prime number y/n

//PRIME NUMBER CHECK

#include <iostream>
using namespace std;

int main()
{
int checknum, remainder;
cout<<"enter num to check"<<endl;
cin>>checknum;
remainder = checknum%2;
cout<<remainder<<endl;
if (remainder==1)
{
  cout<<"Prime"<<endl;
}
else if (remainder == 0)
{
  cout<<"not prime"<<endl;
}
else
{
  cout<<"error"<<endl;
}
}