Programs to check if a number is a perfect number or not have been shown here. A perfect number is a positive integer that is equal to the sum of its proper divisors. For example 6 is a perfect number because if we add it's proper divisors (1, 2 and 3), we get 6 i.e. 1 + 2+ 3 = 6. Some of the other perfect numbers are 28, 496, 8128 etc.

#### Page content(s):

1. Program & output

## 1.1. C Program to Check If a Number is a Perfect Number or Not

Code has been copied
/**************************
alphabetacoder.com
C program to check if a
number is a perfect number
***************************/

#include <stdio.h>

int main() {
// declare variables
int n, i, sum = 0;

// take input
printf("Enter the number: ");
scanf("%d", & n);

// add all the divisor upto n / 2
for (i = 1; i <= (n / 2); i++) {
if (n % i == 0)
sum = sum + i;
}

// check if the input number
// is equal to the sum
if (n == sum)
printf("%d is a perfect number", n);
else
printf("%d is not a perfect number", n);

return 0;
}


Output

#### Case 1:

Enter the number: 6

6 is a perfect number

#### Case 2:

Enter the number: 10

10 is not a perfect number

#### Case 3:

Enter the number: 28

6 is a perfect number