Check If a Number is a Perfect Number or Not

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

1. Program to Check If a Number is a Perfect Number or Not

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