Harshad Number in Java

In this post, we will develop a Java program to check whether the given number is a Harshad number or not? We will also find all Harshad number which belongs to a given range. Later we will develop another Java program to check multiple Harshad numbers.

In mathematics, a Harshad number in a given number base is an integer that is divisible by the sum of its digits when written in that base. The Harshad number is also called a Niven number. It is named after D. R. Kaprekar.

Java program to check the given number is Harshad number or not

import java.util.Scanner;

public class HarshadNumber {

   // method to check number is 
   // harshad number or not
   public static boolean isHarshad(int number) {

      // calculate sum of digits of the number
      int digitSum = sumOfDigits(number);

      if(number % digitSum == 0)
         return true;

      return false;
   }

   private static int sumOfDigits(int number) {

      int sum = 0;

      while(number != 0) {
        // add last digit to sum
        sum += number%10;

        // remove last digit
        number /= 10;
      }

      return sum;
   }

   public static void main(String[] args) {

      // declare variables
      int number = 0;
      boolean result = false;

      //create Scanner class object to take input
      Scanner scan = new Scanner(System.in);

      // take input from end-user
      System.out.print("Enter an integer number:: ");
      number = scan.nextInt();

      // check number is harshad number or not
      result = isHarshad(number);
      if(result)
      System.out.println(number +
                  " is a Harshad number");
      else
      System.out.println(number +
                  " is not a Harshad number");

      // close Scanner class object
      scan.close();
   }
}

The output for the different test-cases:-

Enter an integer number:: 9
9 is a Harshad number

Enter an integer number:: 11
11 is not a Harshad number

Enter an integer number:: 378
378 is a Harshad number

Also see:- Special number, Magic number, Armstrong number, Perfect number, Evil Number, Spy Number, Sunny number in Java

Java program to find all Harshad number in a given range

import java.util.Scanner;

public class HarshadNumberInRange {

   // method to check number is 
   // Harshad number or not
   public static boolean isHarshad(int number) {

      // calculate sum of digits of the number
      int digitSum = sumOfDigits(number);

      if(number % digitSum == 0)
         return true;

      return false;
   }

   // method to find sum of digits
   private static int sumOfDigits(int number) {
      int sum = 0;

      while(number != 0) {
         // add last digit to sum
         sum += number%10;

         // remove last digit
         number /= 10;
      }

      return sum;
   }

   public static void main(String[] args) {

      // declare variables
      int minRange = 0, maxRange = 0;

      // create Scanner class object
      Scanner scan = new Scanner(System.in);

      // read inputs
      System.out.print("Enter min value of range:: ");
      minRange = scan.nextInt();
      System.out.print("Enter max value of range:: ");
      maxRange = scan.nextInt();

      // find all harshad number
      System.out.println("The Harshad numbers from "+
                minRange+" to "+ maxRange+" are:: ");

      for(int i=minRange; i<=maxRange; i++) {
         if(isHarshad(i))
            System.out.print(i+" ");
      }

      // close Scanner class object
      scan.close();
   }
}

Output:-

Enter min value of range:: 1
Enter max value of range:: 100
The Harshad numbers from 1 to 100 are::
1 2 3 4 5 6 7 8 9 10 12 18 20 21 24 27 30 36 40 42 45 48 50 54 60 63 70 72 80 81 84 90 100

Multiple Harshad number in Java

When a Harshad number is divided by the sum of digits and produces another Harshad number then the number is called a Multiple Harshad number. Examples of Multiple Harshad numbers are:- 7, 21, 378, and 6804

Example:-
number = 6804
Sum of digits = 6+8+0+4 = 18
6804 / 18 = 378, so 6804 is a Harshad number.
Now, the sum of digits of 378 = 18
378 / 18 = 21 So, 378 is also a Harshad number.

Hence the number 6804 is a multiple Harshad number.

Java program to check multiple Harshad number

import java.util.Scanner;

public class MultipleHarshadNumber {

   // method to check number is 
   // harshad number or not
   public static boolean isHarshad(int number) {

      // calculate sum of digits of the number
      int digitSum = sumOfDigits(number);

      if(number % digitSum == 0)
         return true;

      return false;
   }

   // method to find sum of digits
   private static int sumOfDigits(int number) {

      int sum = 0;
      while(number != 0) {
         // add last digit to sum
         sum += number%10;

         // remove last digit
         number /= 10;
      }

      return sum;
   }

   // method to check number is 
   // multiple Harshad number or not
   public static boolean isMultipleHarshad(int number) {

      // first of all check the given 
      // number is harshad number or not
      if(! isHarshad(number))
      return false;

      // find sum of digits
      int sum = sumOfDigits(number);

      // find result after dividing 
      // by the sum of digits
      int newNumber = number/sum;

      // check new number is harshad number
      if(isHarshad(newNumber))
      return true;

      return false;
   }

   public static void main(String[] args) {

      // declare variables
      int number = 0;
      boolean result = false;

      //create Scanner class object to take input
      Scanner scan = new Scanner(System.in);

      // take input from end-user
      System.out.print("Enter an integer number:: ");
      number = scan.nextInt();

      // check number is Harshad number or not
      result = isHarshad(number);

      // display result
      if(result)
      System.out.println(number +
           " is a multiple Harshad number");
      else
      System.out.println(number +
           " is not a multiple Harshad number");

      // close Scanner class object
      scan.close();
   }
}

Output:-

Enter an integer number:: 21
21 is a multiple Harshad number

Enter an integer number:: 6805
6805 is not a multiple Harshad number

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