C Program to Check Perfect Number

Posted in C Tutorial

Updated on Jan 10, 2024

By Mari Selvan

👁️ 109 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

In the realm of programming, exploring the properties of numbers is a fascinating task. One such special type of number is a perfect number.

A perfect number is a positive integer that is equal to the sum of its proper divisors (excluding itself).

In this tutorial, we will delve into a C program designed to check whether a given number is a perfect number.

The program involves finding the sum of the proper divisors and comparing it with the original number.

📄 Example

Let's delve into the C code that accomplishes this task.

isPerfectNumber.c

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#include <stdio.h>

// Function to check if a number is a perfect number
int isPerfectNumber(int number) {
  int sum = 0;

  // Iterate through potential divisors up to number/2
  for (int i = 1; i <= number / 2; ++i) {
    // Check if i is a divisor of the number
    if (number % i == 0) {
      sum += i; // Add the divisor to the sum
    }
  }

  // If the sum of divisors is equal to the number, it is a perfect number
  return (sum == number);
}

// Driver program
int main() {
  // Replace this value with the number you want to check
  int number = 28;

  // Call the function to check if the number is a perfect number
  if (isPerfectNumber(number))
    printf("%d is a perfect number.\n", number);
  else
    printf("%d is not a perfect number.\n", number);

  return 0;
}

💻 Testing the Program

To test the program with different numbers, modify the value of number in the main program.

Output

28 is a perfect number.

Compile and run the program to check if the specified number is a perfect number.

🧠 How the Program Works

The program defines a function isPerfectNumber that takes an integer number as input and returns 1 (true) if the number is a perfect number, and 0 (false) otherwise.
Inside the main program, replace the value of number with the desired number you want to check.
The program calls the isPerfectNumber function and prints the result.

📏 Between the Given Range

Let's delve into the C code that identifies perfect numbers in the specified range.

isPerfectNumber.c

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#include <stdio.h>

// Function to check if a number is perfect
int isPerfectNumber(int num) {
  int sum = 0;
  for (int i = 1; i <= num / 2; ++i) {
    if (num % i == 0) {
      sum += i;
    }
  }
  return (sum == num);
}

// Driver program
int main() {
  printf("Perfect Numbers in the range 1 to 50:\n");

  for (int i = 1; i <= 50; ++i) {
    if (isPerfectNumber(i)) {
      printf("%d ", i);
    }
  }

  printf("\n");

  return 0;
}

💻 Testing the Program

Output

Perfect Numbers in the range 1 to 50:
6 28

To test the program, simply compile and run it. The output will display the perfect numbers in the range from 1 to 50.

🧠 How the Program Works

The program defines a function isPerfectNumber that checks if a given number is a perfect number.
Inside the function, it iterates through numbers from 1 to half of the given number, summing up the proper divisors.
The main function tests the range from 1 to 50 and prints the perfect numbers.

🧐 Understanding the Concept of Perfect Number

Before delving into the code, let's understand the concept of perfect numbers. A perfect number is a positive integer that is equal to the sum of its proper divisors (excluding itself).