Program to check whether a number is perfect or not in C

Logic:

• Perfect Number A number is perfect if sum of its divisors other than the number is the number itself.
• Enter the number n
• Example 1: n=6
• We will check whether number is divisible by any number from 1 to n-1 here 5.
• 6 is divisibly by 1,2,3 (Don’t include number itself ie. 6 in its divisors)
• sum=1 + 2 + 3 =6=number itself
• So It is a perfect number
• Example 2: n=7
• We will check whether number is divisible by any number from 2 to n-1 here 6.
• 7 is divisibly by 1 only (Don’t include number itself ie. 7 in its divisors)
• sum=1 which is not equal to 7
• So It is not a perfect number

Algorithm

1. Enter the number as n
2. for (i = 1; i <= n – 1; i++)
3. if (n % i == 0)
4. s = s + i;
6. if (s == n)
7. printf(“It is perfect number”);
8. else
9. printf(“It is not perfect number”);

Program

#include <stdio.h>

int main()
{
    printf("****************************************************");
    printf("\n****************************************************");
    printf("\n**      WAP to check a number for perfect         **");
    printf("\n**               Created by Sheetal Garg          **");
    printf("\n**               Assistant Professor              **");
    printf("\n**               Phone No:9467863365              **");
    printf("\n****************************************************");
    printf("\n******************************************************\n");
    int n, i, s = 0;
    printf("enter number");
    scanf("%d", &n);
    for (i = 1; i <= n - 1; i++)
        if (n % i == 0)
            s = s + i;
    if (s == n)
        printf("It is perfect number");
    else
        printf("It is not perfect number");
    return 0;
}

Output 1

***************************************************************************
***************************************************************************
**                    WAP to check a number for perfect                  **
**                          Created by Sheetal Garg                      **
**                            Assistant Professor                        **
**                            Phone No:9467863365                        **
***************************************************************************
***************************************************************************
enter number
6
It is perfect number

Output 2

***************************************************************************
***************************************************************************
**                    WAP to check a number for perfect                  **
**                          Created by Sheetal Garg                      **
**                            Assistant Professor                        **
**                            Phone No:9467863365                        **
***************************************************************************
***************************************************************************
enter number
7
It is not perfect number