Highly divisible triangular number | Project Euler | Problem #12

URL to the problem page: https://projecteuler.net/problem=12

The sequence of triangle numbers is generated by adding the natural numbers. So the 7^th triangle number would be 1 + 2 + 3 + 4 + 5 + 6 + 7 = 28. The first ten terms would be:

1, 3, 6, 10, 15, 21, 28, 36, 45, 55, ...

Let us list the factors of the first seven triangle numbers:

1: 1
3: 1,3
6: 1,2,3,6
10: 1,2,5,10
15: 1,3,5,15
21: 1,3,7,21
28: 1,2,4,7,14,28

We can see that 28 is the first triangle number to have over five divisors.

What is the value of the first triangle number to have over five hundred divisors?

#include <iostream>

using namespace std;

int main()

{

    long long i = 1, j, number = 0, counter = 1, a;

    while (true) {

        number = 0;

        counter = 0;

        for (j = 0; j <= i; j++) {

            number += j;

        }

        for (j = 2; j <= sqrt(number); j++) {

            a = number / j;

            if (number % a == 0) {

                counter++;

            }

        }

        counter *= 2;

        counter++;

        if (counter > 500) {

            cout << "Value of the first triangle number to have over five hundred divisors is  =  " << number << endl;

            break;

        }

        i++;

    }

}

CLICK TO SEE THE OUTPUT.