Java Program to Check Perfect Number

Posted in Java Tutorial

Updated on Oct 30, 2024

By Mari Selvan

👁️ 95 - 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 Java program designed to check whether a given number is a perfect number.

The program involves finding the divisors of a number and determining if their sum equals the original number.

📄 Example

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

PerfectNumberChecker.java

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import java.util.Scanner;

public class PerfectNumberChecker {

  // Function to check if a number is a perfect number
  static boolean isPerfectNumber(int number) {
    int sum = 1; // Start with 1 as every number is divisible by 1

    // Iterate from 2 to the square root of the number
    for (int i = 2; i * i <= number; i++) {
      if (number % i == 0) {
        // If i is a divisor, add i and its counterpart to the sum
        sum += i;
        if (i * i != number) {
          sum += number / i;
        }
      }
    }

    // If the sum equals the original number, it is a perfect number
    return sum == number;
  }

  // Driver program
  public static void main(String[] args) {
    // Replace this value with the number you want to check
    Scanner scanner = new Scanner(System.in);
    System.out.print("Enter a number: ");
    int number = scanner.nextInt();

    // Call the function to check if the number is a perfect number
    if (isPerfectNumber(number)) {
      System.out.println(number + " is a perfect number.");
    } else {
      System.out.println(number + " is not a perfect number.");
    }
  }
}

💻 Testing the Program

To test the program with different numbers, enter a new value when prompted.

Output

Enter a number: 28
28 is a perfect number.

🧠 How the Program Works

The program defines a class PerfectNumberChecker containing a static method isPerfectNumber that takes an integer number as input and returns true if the number is a perfect number, and false otherwise.
Inside the main method, replace the value of number with the desired number you want to check.
The program calls the isPerfectNumber method and prints the result.

📏 Between the Given Range

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

PerfectNumberChecker.java

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public class PerfectNumberChecker {

  // Function to check if a number is perfect
  static boolean isPerfectNumber(int num) {
    int sum = 1; // Start with 1 as every number is divisible by 1

    for (int i = 2; i <= Math.sqrt(num); i++) {
      if (num % i == 0) {
        sum += i;
        if (i != num / i) {
          sum += num / i;
        }
      }
    }

    return sum == num;
  }

  // Driver program
  public static void main(String[] args) {
    System.out.println("Perfect Numbers in the range 1 to 50: ");

    for (int i = 2; i <= 50; i++) {
      if (isPerfectNumber(i)) {
        System.out.print(i + " ");
      }
    }

    System.out.println();
  }
}

💻 Testing the Program

Output

Perfect Numbers in the range 1 to 50:
6 28

Compile and run the program to see the perfect numbers in the specified range.

🧠 How the Program Works

The program defines a class PerfectNumberChecker containing a static method isPerfectNumber to check if a number is perfect.
Inside the method, it iterates through divisors up to the square root of the number and calculates the sum of proper divisors.
The main method tests for perfect numbers in the range from 1 to 50 and prints the results.

🧐 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).