Check whether a number is a Perfect number or not with C.

/*
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.
*/

#include <stdio.h>
int main()
{
int i, num, sum = 0;

printf("Enter any number to check perfect number: ");
scanf("%d", &num);

for (i = 1; i <= num / 2; i++)
{
if (num % i == 0)
{
    sum += i;
}
}
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