Euler project. Task number 3. Where is the mistake?

Question

C++ / C#

I am new to programming. I decided for the experience to solve problems from the Euler project.
3 problem is not solved.
Condition: "The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of 600851475143?"
Here is the code:

#include <iostream>
using namespace std;

long long number = 600851475143;
int del = 0;

int main(int argc, char const *argv[])
{
  for (int i = 2; i < number; i++)
  {
    if (number % i == 0)
    {
      for (int j = 2; j < i; j++)
      {
        if (i % j == 0)	
          break;
        else
          del = i;	
      }	
    }
  }	
  cout << del << endl;
  return 0;
}

Answer 1

Your number doesn't fit in int. And you drive the loop from 2 to number. Your condition i < numberin the loop will always be fulfilled - because well, int i cannot be greater than number.
edit: And in general, the logic of checking for simplicity is broken. del = iholds for any j such that i is not divisible by it. Those. if i=6, then with j=5 you will overwrite del. You need to set the bool flag in the loop. And, after the cycle, look at it.