Perfect Number or Not in C Program

Perfect number or not in c program.

In this article, you will learn how to check whether a given number is a perfect number.

What is the perfect number?

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

Example-1 A Perfect Number

There are three ways to solve this problem:

1. Using while loop
2. Using do-while loop
3. Using for loop

You should know about the following topics in C programming to understand this program:

• If-else statement
• While loop in C
• Do-while loop in C
• For loop in C

1 - Perfect Number or Not in C using While loop

// Perfect Number or Not in C using While loop
#include <stdio.h>

// It's the main function of the program
int main()
{
    int num, result = 0;

    // Step-1 Take input from the User
    printf("INPUT A NUMBER: ");
    scanf("%d", &num);

    // Step-2 Check input number should be positive
    if (num > 0)
    {
        // Step-3 Use a loop to find the perfect number
        int i = 1;
        while (i <= num)
        {
            if (num % i == 0)
                result += i;
            i++;
        }

        // Step-3 Check the Result(sum of factors) == 2*Input Number
        if (result == 2 * num)
            printf("%d IS A PERFECT NUMBER.\n", num);
        else
            printf("%d IS NOT A PERFECT NUMBER.\n", num);
    }
    else
        printf("Enter a positive number!\n");

    return 0;
}

Run

Output

2 - Perfect Number or Not in C using Do-while loop

// Perfect Number or Not in C using Do-while loop
#include <stdio.h>

// It's the main function of the program
int main()
{
    int num, result = 0;

    // Step-1 Take input from the User
    printf("INPUT A NUMBER: ");
    scanf("%d", &num);

    // Step-2 Check input number should be positive
    if (num > 0)
    {
        // Step-3 Use a loop to find the perfect number
        int i = 1;
        do
        {
            if (num % i == 0)
                result += i;
            i++;
        } while (i <= num);

        // Step-3 Check the Result(sum of factors) == 2*Input Number
        if (result == 2 * num)
            printf("%d IS A PERFECT NUMBER.\n", num);
        else
            printf("%d IS NOT A PERFECT NUMBER.\n", num);
    }
    else
        printf("Enter a positive number!\n");

    return 0;
}

Run

Output

3 - Perfect Number or Not in C using For loop

// Perfect Number or Not in C using For loop
#include <stdio.h>

// It's the main function of the program
int main()
{
    int num, result = 0;

    // Step-1 Take input from the User
    printf("INPUT A NUMBER: ");
    scanf("%d", &num);

    // Step-2 Check input number should be positive
    if (num > 0)
    {
        // Step-3 Use a loop to find the perfect number
        for (int i = 1; i <= num; i++)
        {
            if (num % i == 0)
                result += i;
        }

        // Step-3 Check the Result(sum of factors) == 2*Input Number
        if (result == 2 * num)
            printf("%d IS A PERFECT NUMBER.\n", num);
        else
            printf("%d IS NOT A PERFECT NUMBER.\n", num);
    }
    else
        printf("Enter a positive number!\n");

    return 0;
}

Run

Output