C program to check whether a number is perfect number or not

Write a program to find whether a given number (say x) is a “perfect number” or not.

Definition of Perfect number:

A perfect number is a positive integer that is equal to the sum of its proper positive divisors excluding the number itself. By this definition, 1 is not a perfect number.

Explanation:

Take number 6.

Proper positive divisors of 6 is 1,2,3 and their sum is 1+2+3=6.
So, 6 is a perfect number.

Input: A single positive number  x

Output:
yes if given number x is a perfect number

no if given number x is not a perfect number

Example 1:

Input: 6

Output: yes

Example 2:

Input: 7

Output: no

Implementation:

#include <stdio.h> int isperfect(int n) { int i; int sum=0; for(i=1;i<n;i++) if(n%i==0) sum+=i; return (sum==n); } int main() { int n; scanf("%d",&n); if(isperfect(n)) printf("yes"); else printf("no"); return 0; }