Neon Number

Last Updated : 19 Jul, 2025

A neon number is a number where the sum of digits of square of the number is equal to the number. The task is to check and print neon numbers in a range.

Examples:

Input : 9
Output : Neon Number
Explanation: square is 9*9 = 81 and 
sum of the digits of the square is 9.
Input :12
Output : Not a Neon Number
Explanation: square is 12*12 = 144 and 
sum of the digits of the square is 9 (1 
+ 4 + 4) which is not equal to 12.

The implementation is simple, we first compute square of given number, the find sum of digits in the square.

C++

// C/C++ program to check and print
// Neon Numbers upto 10000
#include <iostream>
using namespace std;
#include <math.h>

int checkNeon(int x)
{
    // storing the square of x
    int sq = x * x;

    // calculating the sum of digits
    // of sq
    int sum_digits = 0;
    while (sq != 0) {
        sum_digits = sum_digits + sq % 10;
        sq = sq / 10;
    }
    return (sum_digits == x);
}

// Driver Code
int main(void)
{
    // Printing Neon Numbers upto 10000
    for (int i = 1; i <= 10000; i++) 
        if (checkNeon(i))
            cout << i << " ";    
}

Java

// Java program to check and print
// Neon Numbers upto 10000
import java.io.*;

class GFG {
    // function to check Neon Number
    static boolean checkNeon(int x)
    {
        // storing the square of x
        int sq = x * x;

        // calculating the sum of digits
        // of sq
        int sum_digits = 0;
        while (sq != 0) {
            sum_digits = sum_digits + sq % 10;
            sq = sq / 10;
        }
        return (sum_digits == x);
    }

    // Driver Code
    public static void main(String args[])
                        throws IOException
    {
        // Printing Neon Numbers upto 10000
        for (int i = 1; i <= 10000; i++) 
            if (checkNeon(i))
                System.out.print(i + " ");        
    }
}
// This code is contributed by Nikita Tiwari.

Python

# Python program to check and print 
# Neon Numbers upto 10000

# function to check Neon Number
def checkNeon (x) :
    # storing the square of x
    sq = x * x
    
    # calculating the sum of digits
    # of sq
    sum_digits = 0
    while (sq != 0) :
        sum_digits = sum_digits + sq % 10
        sq = sq / 10
    
    return (sum_digits == x)

# Driver Code

i = 1
# Printing Neon Numbers upto 10000
while i <= 10000 :
    if (checkNeon(i)) :
        print i,
    i = i + 1

# This code is contributed by Nikita Tiwari.

// C# program to check and print
// Neon Numbers upto 10000
using System;

class GFG 
{
    // function to check Neon Number
    static bool checkNeon(int x)
    {
        // storing the square of x
        int sq = x * x;

        // calculating the sum of digits
        // of sq
        int sum_digits = 0;
        while (sq != 0) 
        {
            sum_digits = sum_digits + sq % 10;
            sq = sq / 10;
        }
        return (sum_digits == x);
    }

    // Driver Code
    public static void Main()
                        
    {
        // Printing Neon Numbers upto 10000
        for (int i = 1; i <= 10000; i++) 
            if (checkNeon(i))
                Console.Write(i + " "); 
    }
}

// This code is contributed by vt_m.

JavaScript

<script>

// Javascript program to check and print
// Neon Numbers upto 10000

    // function to check Neon Number
    function checkNeon(x)
    {
        // storing the square of x
        let sq = x * x;

        // calculating the sum of digits
        // of sq
        let sum_digits = 0;
        while (sq != 0) {
            sum_digits = sum_digits + sq % 10;
            sq = Math.floor(sq / 10);
        }
        return (sum_digits == x);
    }

// driver program

       // Printing Neon Numbers upto 10000
        for (let i = 1; i <= 10000; i++) 
            if (checkNeon(i))
                document.write(i + " ");
        
</script>

PHP

<?php
// PHP program to check and print
// Neon Numbers upto 10000

function checkNeon($x)
{
    
    // storing the square of x
    $sq = $x * $x;

    // calculating the  
    // sum of digits of sq
    $sum_digits = 0;
    while ($sq != 0) 
    {
        $sum_digits = $sum_digits + 
                         $sq % 10;
        $sq = $sq / 10;
    }
    return ($sum_digits == $x);
}

    // Driver Code
    // Printing Neon Numbers
    // upto 10000
    for ($i = 1; $i <= 10000; $i++) 
        if (checkNeon($i))
            echo $i . " "; 
            
// This code is contributed by Sam007
?>

Output:

1 9

Javascript Program For Removing Duplicates From A Sorted Linked List

Nikita tiwari

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