Perfect Number Checker

```﻿using System;

namespace Algorithms.Numeric
{
/// <summary>
///     In number theory, a perfect number is a positive integer that is equal to the sum of its positive
///     divisors, excluding the number itself.For instance, 6 has divisors 1, 2 and 3 (excluding
///     itself), and 1 + 2 + 3 = 6, so 6 is a perfect number.
/// </summary>
public static class PerfectNumberChecker
{
/// <summary>
///     Checks if a number is a perfect number or not.
/// </summary>
/// <param name="number">Number to check.</param>
/// <returns>True if is a perfect number; False otherwise.</returns>
/// <exception cref="ArgumentException">Error number is not on interval (0.0; int.MaxValue).</exception>
public static bool IsPerfectNumber(int number)
{
if (number < 0)
{
throw new ArgumentException(\$"{nameof(number)} cannot be negative");
}

var sum = 0; /* sum of its positive divisors */
for (var i = 1; i < number; ++i)
{
if (number % i == 0)
{
sum += i;
}
}

return sum == number;
}
}
}
```