Here in this tutorial you will learn how to check a neon number in Java.

**What is a Neon Number?**

Neon numbers are those numbers whose sum of the digits when squared is exactly the same as the number itself.

For example, the number **9**.

Now the square of the number, **9** is **81**. The sum of the digits in the square, 81 is 8 + 1 = 9, which is equal to the number itself.

Hence, the number 9 is a Neon number.

However, let the number is **11.**

Now the square of the number, **11** is **121**. The sum of the digits in the square, 121 is 1 + 2 + 1 = 4, which is not equal to the number itself.

Hence, the number 11 is NOT a Neon number.

Below is a program that inputs a number, and checks whether it is a Neon number or not.

## Java Program to Check Neon Number

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import java.util.Scanner; public class NeonNumber { static void checkForNeon(int number) { int square = number*number; int sumOfDigits = 0; while(square != 0) { sumOfDigits += square % 10; square = square/10; } if(sumOfDigits == number) System.out.println("The number is a Neon number"); else System.out.println("The number is not a Neon number"); } public static void main (String[] args) { Scanner input = new Scanner(System.in); System.out.print("Enter a Number: "); int number = input.nextInt(); checkForNeon(number); } } |

**Output:**

*Enter a Number: 9*

*The number is a Neon number*

The program runs a while loop to calculate the sum of the digits of the input number’s square.

Remember, *sumOfDigits += square / 10;* is the same as *sumOfDigits = sumOfDigits + square / 10;*

The program then just compares and see if the sum is in fact equal to the number itself.

There are only three neon numbers though: 0, 1 and 9.