# C Exercises: Check whether a given number is a perfect number or not

## C For Loop: Exercise-27 with Solution

Write a C program to check whether a given number is a 'Perfect' number or not.

**Visual Presentation:**

**Sample Solution:**

**C Code:**

```
/*
Perfect number is a positive number which sum of all positive divisors excluding that number is equal to that number.
For example, 6 is a perfect number since the divisors of 6 are 1, 2, and 3. Sum of its divisors is 1 + 2 + 3 = 6
*/
#include <stdio.h> // Include the standard input/output header file.
int main()
{
int n, i, sum; // Declare variables for user input, loop control, and sum.
printf("Input the number: "); // Prompt the user for input.
scanf("%d", &n); // Read the value of 'n' from the user.
sum = 0; // Initialize the sum variable.
printf("The positive divisors: "); // Print a message to indicate positive divisors are being displayed.
for (i = 1; i < n; i++) // Loop to find and display positive divisors.
{
if (n % i == 0) // If 'i' is a divisor of 'n'.
{
sum = sum + i; // Add 'i' to the sum.
printf("%d ", i); // Print 'i' as a positive divisor.
}
}
printf("\nThe sum of the divisors is: %d", sum); // Print the sum of the divisors.
if (sum == n) // Check if the sum of divisors is equal to the original number.
printf("\nSo, the number is perfect.\n"); // If true, print that the number is perfect.
else
printf("\nSo, the number is not perfect.\n"); // If false, print that the number is not perfect.
return 0; // Return 0 to indicate successful execution.
}
```

Sample Output:

Input the number : 56 The positive divisor : 1 2 4 7 8 14 28 The sum of the divisor is : 64 So, the number is not perfect.

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**Previous:** Write a program in C to find the sum of the series 1 +11 + 111 + 1111 + .. n terms.

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