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.

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
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