In this C# program, we will learn how to write a program to check whether the entered number is a ** perfect number** or not.

A * perfect number *is a positive integer that is equal to the sum of its positive divisors, excluding the number itself.

* For Example*, 6 has divisors 1, 2 and 3 (excluding itself), and 1 + 2 + 3 = 6, so 6 is a perfect number.

The sum of divisors of a number, excluding the number itself, is called its **aliquot sum**, so a perfect number is one that is equal to its aliquot sum. In other words, a * perfect number* is a number that is half the sum of all of its positive divisors including itself

I.e. *σ**1**(n) = 2n*

* For Example*, 28 is perfect as 1 + 2 + 4 + 7 + 14 + 28 = 56 = 2 × 28

Here is the code of the program to check whether the entered number is a perfect number or not:

```
using System;
namespace TutorialsrackPrograms
{
class Program
{
//C# Program to Check Whether the Entered Number is a Perfect Number or Not.
static void Main(string[] args)
{
int number, sum = 0, n;
Console.Write("Enter The Number: ");
number = int.Parse(Console.ReadLine());
n = number;
for (int i = 1; i < number; i++)
{
if (number % i == 0)
{
sum = sum + i;
}
}
if (sum == n)
{
Console.WriteLine("\nEntered Number is a Perfect Number");
}
else
{
Console.WriteLine("\nEntered Number is not a Perfect Number");
}
Console.Read();
}
}
}
```

Enter The Number: 28

Entered Number is a Perfect Number

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