Help optimizing code

Question

I have written a prime number program, which shows prime numbers , quantity of prime numbers and sum of prime numbers

Answer 1

Hint: What if i = 5?

Answer 2

#include <iostream>
using namespace std;
int main()

{
    int upperlimit = 0;
    int lowerlimit = 0;
    int count = 0;
    int sum = 0;

    cout << "Please enter upper limit: ";
    cin>>upperlimit;

    cout << "Please enter  lower limit: ";
    cin>>lowerlimit;

    if (lowerlimit>1)
    {
       for (int i=lowerlimit; i<=upperlimit; i++)
       {
           if((i%2) !=0 && (i%3) !=0)
           {
              count++;
              sum = sum + i;
              cout<<i<<" ";

                    }
           } 
           cout <<"\n total prime number : "<<count<<endl;
           cout <<"\n sum of prime number: "<<sum<<endl;

                   }

                   if (lowerlimit>upperlimit)
                   {
                    cout<<"Lower limit cannot be greater than upper limit";

                                            }
                                            if (upperlimit <2)
                                            {
                                                          cout<<" upper limit cannot be less  than 2";
                                                 }

}

Answer 3

5 in place of 3 in AND operator