Q. C++ Program to Check Whether the Given Number Is Perfect Number or Not.

Here you will find an algorithm and program in C++ programming language to check whether the given number is perfect number or not. First let us understand what Perfect number means.

Explanation : Perfect number is a positive integer equal to the sum of its proper divisors.

For Example : 6 is perfect number because sum of its proper divisor(1, 2, 3) is equal to 6.

START
Step 1 - Input the number.
Step 2 - Find all divisors of the number except the number itself.
Step 3 - If the sum of all divisors of the number is equal to the number, then return true. Else, return false.
STOP

C++ Program to Check Perfect Number

#include <iostream>
using namespace std; 
int main(){
  int num=28,i=1,sum=0;
  while(i<num){
    if(num%i==0)
      sum=sum+i;
    i++; 
  }
  if(sum==num)
    cout << i << " is a perfect number\n"; 
  else
    cout << i << " is not a perfect number\n";
  return 0;
}

Output

28 is a perfect number.