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### Perfect Number Program in C, C++

Write a C, C++ program to check whether a given number is perfect or not. We have to write a program to check whether a input number is perfect.

Perfect Number

A perfect number, is a positive integer that is equal to the sum of its proper divisors.

For example - 6 is a perfect number.

6  = 1 + 2 + 3 (1,2,3 is it's factors).

Similarly 28 is a perfect number.

28 = 1 + 2 + 4 + 7 + 14

Let's take another example of 12. Factors of 12 is 1, 2, 3, 4, 6.

1 + 2 + 3+ 4 + 6 = 16. So we can conclude that 12 is not a perfect number.

Print factors of a number

C, C++ Interview Questions

Print prime numbers between 1 to 100

## Perfect Number Program in C

```#include <stdio.h>

int main(void) {

int num, i=1, sum=0;

printf("Enter number \n");
scanf("%d",&num);

/* Check if entered number is greater than zero. */

if( num > 0){

while(i < num){

if(num % i==0){
sum = sum + i;
}

i++;
}

/* If entered number is equal to it's proper divisiors. */

if(sum == num){

printf("\n %d is a perfect number",i);

} else {

printf("\n %d is not a perfect number",i);

}

} else {

printf("Perfect number should be greater than zero");

}

return 0;
}

```
Output :

Enter number : 6

6 is a perfect number

Enter number : 23

23 is not a perfect number

## Perfect Number Program in C++

```#include <iostream>
using namespace std;

int main() {

int num, sum = 0;

cout << " Enter a number to check whether it's a perfect or not \n";
cin >> num;

for (int i = 1; i < num; i++) {

if (num % i == 0) {

sum = sum + i;

}
}

if ( sum == num) {

cout << num << " is a Perfect number";

} else {

cout << num << " is not a Perfect number";

}

return 0;
}
```