Example
Input
Input any number: 6
Output
6 is PERFECT NUMBER
Perfect number is a positive integer which is equal to the sum of its proper positive divisors.
For example: 6 is the first perfect number
Proper divisors of 6 are 1, 2, 3
Sum of its proper divisors = 1 + 2 + 3 = 6.
Hence 6 is a perfect number.
/**
* C program to check whether a number is Perfect number or not
*/
#include <stdio.h>
int main()
{
int i, num, sum = 0;
/* Input a number from user */
printf("Enter any number to check perfect number: ");
scanf("%d", &num);
/* Calculate sum of all proper divisors */
for(i = 1; i <= num / 2; i++)
{
/* If i is a divisor of num */
if(num%i == 0)
{
sum += i;
}
}
/* Check whether the sum of proper divisors is equal to num */
if(sum == num && num > 0)
{
printf("%d is PERFECT NUMBER", num);
}
else
{
printf("%d is NOT PERFECT NUMBER", num);
}
return 0;
}
/*
Output :
Enter any number to check perfect number: 6
6 is PERFECT NUMBER
*/