How to Check Whether a Number is Krishnamurthy Number or Not in Java?

Krishnamurthy number can be defined as a number when the sum of the factorial of all digits is equal to the original number.

This Krishnamurthy number is also called the Strong number, Special number and Peterson number.

To show you some instances

Instance-1

Input number is 1

Let’s check it by using the logic of Krishnamurthy number −

1 = 1! = 1 which is equal to the original number.

Hence, 1 is a Krishnamurthy number.

Instance-2

Input number is 145

Let’s check it by using the logic of Krishnamurthy number −

145 = 1!  + 4! + 5! = 1 + 24 + 120 = 145 which is equal to the original number.

Hence, 145 is a Krishnamurthy number.

Instance-3

Input number is 55

Let’s check it by using the logic of Krishnamurthy number −

55 = 5!  +  5! = 120 + 120 = 240 which is not equal to the original number.

Hence, 55 is not a Krishnamurthy number.

Some of other examples of Krishnamurthy numbers include 2, 40585 etc.

Algorithm

• Step 1 − Get an integer number either by initialization or by user input.

• Step 2 − Keep a copy of the original number to compare it with the new number.

• Step 3 − Find the factorial of each digit of the input number and keep a track of the sum of the factorial of the digits.

• Step 4 − At last, compare the sum of the factorial of the digits with the copy of the original input number. If both are equal then it is a Krishnamurthy number. Otherwise the input number is not a Krishnamurthy number.

Multiple Approaches

We have provided the solution in different approaches.

• By Using Static Input Value

• By Using User Defined Method

Let’s see the program along with its output one by one.

Approach-1: By Using User Input Value

In this approach, an integer value will be initialized in the program and then by using the algorithm we can check whether a number is a Krishnamurthy number or not.

Example

import java.util.*;

public class Main {
   //main method
   public static void main(String[] args) {
      //initialized a number
      int originalNumber = 145;
      //printing the given number
      System.out.println("Given number: "+originalNumber);
        
      //keep a copy of original number
      int copyOfOriginalNumber = originalNumber;
      //initializing sum value as 0 
      int sum = 0;
      //continue the while loop till the original number becomes 0
      while (originalNumber != 0) {
         //find the digit of the number
         int digit = originalNumber%10;
         //declare an integer variable say fact & initialize as 1
         int fact = 1; 
         //find the factorial by using for loop
         for (int i= 1; i<= digit; i++){
            fact = fact * i;
         }
         //add the factorial with sum
         sum = sum + fact;
         //get the updated number
         originalNumber = originalNumber / 10;
      }
      //If sum of factorials and original input number 
      //are equal then it is a Krishnamurthy number
      if (sum == copyOfOriginalNumber)
         System.out.println(copyOfOriginalNumber + " is a Krishnamurthy number");
      //print it is not a Krishnamurthy number
      else
         System.out.println(copyOfOriginalNumber + " is not a Krishnamurthy number");
   }
}

Output

Given number: 145
145 is a Krishnamurthy number

Approach-2: By Using User Defined

In this approach the user will be asked to take the input of an integer value and then we will call a user defined method by passing this input number as parameter.

Inside the method we will check whether a number is a Krishnamurthy number or not by using the algorithm.

Example

import java.util.*;

public class Main {
   //main method
   public static void main(String[] args){
      //initialized a number
      int originalNumber = 40585;
      //printing the given number
      System.out.println("Given number: "+originalNumber);
      //keep a copy of original number
      int copyOfOriginalNumber = originalNumber;
      //calling the method to check Krishnamurthy number
      if (checkKrishnamurthy(originalNumber)) 
         System.out.println(copyOfOriginalNumber + " is a Krishnamurthy number"); 
      else
         System.out.println(copyOfOriginalNumber + " is not a Krishnamurthy number"); 
   }
   
   //user defined method 
   public static boolean checkKrishnamurthy(int originalNumber){
      //keep a copy of original number
      int copyOfNumber = originalNumber;
        
      //initializing sum value as 0 
      int sum = 0;
      //continue the while loop till the original number becomes 0
      while(originalNumber>0){
         //find the digit 
         int digit=originalNumber%10;
         //find factorial by calling the user defined method findFactorial() 
         //And add it to sum
         sum=sum+findFactorial(digit);
         originalNumber=originalNumber/10;
      }
      //If sum of factorials and original input number 
      //are equal then return true
      if (sum == copyOfNumber)
         return true;
         //else return false
      else
         return false;
   } 
   //find the factorial of an integer
   public static int findFactorial(int num){
      //declare an integer variable say fact & initialize as 1
      int factorial=1;
      //continue loop till number reaches 1
      while(num>=1){
         //multiply number with factorial
         factorial=factorial*num;
         //decrement the number
         num--;
      }
      //return the factorial
      return factorial;
   }
}

Output

Given number: 40585
40585 is a Krishnamurthy number

In this article, we explored how to check a number whether it is a Krishnamurthy number or not in Java by using different approaches.