Why does the program return a negative number when raising the number 17 to the power of 5?

Question

C++ / C#

Perhaps someone will find the question ridiculous, but when raising the number 17 to the power of 5, the program returns a negative number. It seems to me that the problem is in memory, but no matter how much free space I allocated, nothing changed. Raised with pow from cmath.

PS I apologize in advance, but I started to learn C++ not long ago.
When you enter the number 17 in "inNums", the output is -2147483648.

#include <iostream>
#include <cmath>

bool testNums(int num) {
  bool test;
  int FLT = pow(5, num) - 5;

  if (FLT % num == 0) {
    test = true;
  }
  else{
    std::cout << false << std::endl;
    return false;	
  }

  if (test == true) {
    std::cout << true << std::endl;
    return true;
  }

}

int main() {
  int inNums;

  while (true) {
    std::cin >> inNums;
    testNums(inNums);
  }

  return 0;
}

Answer 1

Integer overflow. Your int is 32 bits, and 5 ¹⁷ = 762939453125 > 2 ³⁹ . Use a 64-bit data type, then you can count up to 5 ²⁷ .

Answer 2

The number -2147483648 looks like an overflow.