Harshad (Or Niven) Number

An integer number in base 10 which is divisible by the sum of its digits is said to be a Harshad Number. An n-Harshad number is an integer number divisible by the sum of its digit in base n.
Below are the first few Harshad Numbers represented in base 10:
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 18, 20………
Given a number in base 10, our task is to check if it is a Harshad Number or not.

Examples :

Input: 3
Output: 3 is a Harshad Number

Input: 18
Output: 18 is a Harshad Number

Input: 15
Output: 15 is not a Harshad Number

1. Extract all the digits from the number using the % operator and calculate the sum. 
2. Check if the number is divisible by the sum.

Below is the implementation of the above idea:

C++

// C++ program to check if a number is Harshad
// Number or not.
#include <bits/stdc++.h>
using namespace std;

// function to check Harshad Number
bool checkHarshad(int n)
{
    // calculate sum of digits
    int sum = 0;
    for (int temp = n; temp > 0; temp /= 10)
        sum += temp % 10;

    // Return true if sum of digits is multiple
    // of n
    return (n % sum == 0);
}

// driver program to check above function
int main()
{
    checkHarshad(12) ? cout << "Yes\n" : cout << "No\n";
    checkHarshad(15) ? cout << "Yes\n" : cout << "No\n";

    return 0;
}

Java

// Java program to check if a number is Harshad
// Number or not

public class GFG {
    // method to check Harshad Number
    static boolean checkHarshad(int n)
    {
        // calculate sum of digits
        int sum = 0;
        for (int temp = n; temp > 0; temp /= 10)
            sum += temp % 10;

        // Return true if sum of digits is multiple
        // of n
        return (n % sum == 0);
    }

    // Driver program to test above functions
    public static void main(String[] args)
    {
        System.out.println(checkHarshad(12) ? "Yes" : "No");
        System.out.println(checkHarshad(15) ? "Yes" : "No");
    }
}

Python3

# Python program to check
# if a number is Harshad
# Number or not.

def checkHarshad( n ) :
    sum = 0
    temp = n
    while temp > 0 :
        sum = sum + temp % 10
        temp = temp // 10
    # Return true if sum of
    # digits is multiple of n
    return n % sum == 0

# Driver Code
if(checkHarshad(12)) : print("Yes")
else : print ("No")

if (checkHarshad(15)) : print("Yes")
else : print ("No")

# This code is contributed
# by Nikita Tiwari

C#

// C# program to check if a number is Harshad
// Number or not
using System;

public class GFG {

    // method to check Harshad Number
    static bool checkHarshad(int n)
    {

        // calculate sum of digits
        int sum = 0;
        for (int temp = n; temp > 0; temp /= 10)
            sum += temp % 10;

        // Return true if sum of digits is
        // multiple of n
        return (n % sum == 0);
    }

    // Driver program to test above functions
    public static void Main()
    {
        Console.WriteLine(checkHarshad(12) ? "Yes" : "No");

        Console.WriteLine(checkHarshad(15) ? "Yes" : "No");
    }
}

// This code is contributed by vt_m.

PHP

<?php
// php program to check if
// a number is Harshad
// Number or not.

// function to check
// Harshad Number
function checkHarshad($n)
{
    // calculate sum of digits
    $sum = 0;
    for ($temp = $n; $temp > 0;
                     $temp /= 10)
        $sum += $temp % 10;

    // Return true if sum of
    // digits is multiple of n
    return ($n % $sum == 0);
}

// Driver Code
$k = checkHarshad(12) ? "Yes\n" : "No\n";
     echo($k);
$k = checkHarshad(15) ? "Yes\n" : "No\n";
     echo($k);

// This code is contributed by ajit.
?>

Javascript

<script>
    // Javascript program to check if a number is Harshad Number or not

    // method to check Harshad Number
    function checkHarshad(n)
    {

        // calculate sum of digits
        let sum = 0;
        for (let temp = n; temp > 0; temp = parseInt(temp / 10, 10))
            sum += temp % 10;

        // Return true if sum of digits is
        // multiple of n
        return (n % sum == 0);
    }

    document.write(checkHarshad(12) ? "Yes" + "</br>" : "No" + "</br>");

      document.write(checkHarshad(15) ? "Yes" + "</br>" : "No" + "</br>");

</script>

Output :

Yes
No

Time complexity: O(log₁₀N) for given input N
Auxiliary space: O(1)

Method #2: Using string:

• We have to convert the given number to a string by taking a new variable.
• Traverse the string, Convert each element to an integer and add this to the sum.
• If the number is divisible by the sum then it is Harshad number.

Below is the implementation of the above approach:

C++

// C++ implementation of above approach
#include<bits/stdc++.h>
using namespace std;

string checkHarshad(int n)
{

    // Converting integer to string
    string st = to_string(n);

    // Initialising sum to 0
    int sum = 0;
    int length = st.length();

    // Traversing through the string
    for(char i : st)
    {

        // Converting character to int
        sum = sum + (i - '0');
    }

    // Comparing number and sum
    if (n % sum == 0)
    {
        return "Yes";
    }
    else
    {
        return "No";
    }
}

// Driver Code
int main()
{
    int number = 18;

    // Passing this number to get result function
    cout << checkHarshad(number) << endl;
}

// This code is contributed by rrrtnx

Java

import java.io.*;
// java code to check the given number is Harshad or not
class GFG
{
  // function to check that given number
  // is Harshad or not.
    static String checkHarshad(int n)
    {

      // converting the integer to string
        String st = Integer.toString(n);
        int sum = 0;

      // calculating total number of digits
      // in a number
        int length=st.length();

      // adding the all digits of a number
        for(int i = 0; i < length; i++){
            sum += st.charAt(i)-'0';
        }

      // checking that sum is divisior of n or not
        if(n % sum == 0){
           return "YES";
        }
        else{
            return "NO";
        }
    }

  // driver code
    public static void main(String args[]){
        int number = 18;

      // function call
        System.out.println(checkHarshad(number));
    }
}

// This code is contributed by Machhaliya Muhammad

Python3

# Python implementation of above approach
def checkHarshad(n):

    # Converting integer to string
    st = str(n)

    # Initialising sum to 0
    sum = 0
    length = len(st)

    # Traversing through the string
    for i in st:

        # Converting character to int
        sum = sum + int(i)

    # Comparing number and sum
    if (n % sum == 0):
        return "Yes"
    else:
        return "No"


# Driver Code
number = 18
# passing this number to get result function
print(checkHarshad(number))

# This code is contributed by vikkycirus

C#

// C# program to find the radii
// of the three tangent circles
// of equal radius when the radius
// of the circumscribed circle is given
using System;

class GFG {
    static String checkHarshad(int n)
    {

        // Converting integer to string
        String st = n.ToString();

        // Initialising sum to 0
        int sum = 0;
        int length = st.Length;

        // Traversing through the string
        foreach(char i in st)
        {
            // Converting character to int
            sum = sum + (i - '0');
        }

        // Comparing number and sum
        if (n % sum == 0) {
            return "Yes";
        }
        else {
            return "No";
        }
    }

    // Driver code
    public static void Main()
    {
        int number = 18;

        // Passing this number to get result function
        Console.WriteLine(checkHarshad(number));
    }
}

// This code is contributed by Nidhi goel

Javascript

<script>
// Javascript implementation of above approach
function checkHarshad(n){

    // Converting integer to string
    let st = String(n)

    // Initialising sum to 0
    let sum = 0
    let length = st.length

    // Traversing through the string
    for(i in st){
        // Converting character to int
        sum = sum + parseInt(i)
    }

    // Comparing number and sum
    if (n % sum == 0){
        return "Yes"
    }
    else{
        return "No"
    }
}

// Driver Code
let number = 18
// passing this number to get result function
document.write(checkHarshad(number))

// This code is contributed by _saurabh_jaiswal
</script>

Output

Yes

Time  Complexity: O(n)
Auxiliary Space: O(n)

References:
https://en.wikipedia.org/wiki/Harshad_number