In this tutorial, we will write a java program to check whether a given number is Tech Number or not. We will also write a program to find all the tech numbers in a given range.

## What is Tech Number?

A number is called** Tech number**, if it has an even number of digits, and when we split the number into two halves then the square of the sum of those halves is equal to the number itself.

For example, 2025 is a Tech number.

To verify whether 2025 is a Tech number, we have split the number in two halves (20 & 25) and then calculated the square of the sum of two halves. It resulted in the number itself, thus we can say that it’s a Tech number.

2025 = (20+25)^2 = (45)^2 = 2025

## Steps that we will use in the Program to check for Tech Number

- Take the number from the user and store it into a variable using Scanner class.
- Check the number of digits in the input number, if the number of digits is not even, the input number is not a Tech number else continue with the next step.
- Split the number in two halves,
`num1`

and`num2`

. - Find the sum of the squares of two halves
`(num1+num2)^2`

, if it is equal to the number itself, return “Tech Number” else return “Not a Tech Number”

## Tech Number Program in Java

Here we are using the steps that we have mentioned above. We took the input number from the user and assigned it to number `n`

and then we copied the value of `n`

to a new variable `num`

. This is because we are going to perform some operations on `num`

and we want to retain the original number for comparison later.

In the next step we calculated the number of digits in the input number using while loop. If number of digits are even we continued to the next step else we returned “Not a Tech number”.

In the next step we split the number in two halves `firstHalf`

and `secondHalf`

. We then calculated the sum of squares of these two halves.

If the sum is equal to the number, the number is a Tech number, else not a Tech number.

import java.util.Scanner; public class JavaExample { public static void main(String args[]) { int n, num, firstHalf, secondHalf, numberOfDigits=0, squareOfTwoHalves; Scanner scan = new Scanner(System.in); System.out.print("Enter the number: "); //Store the input number into variable num n = scan.nextInt(); //copying the value of n into a new variable num num = n; //Here we are finding the number of digits in the input number while (num > 0) { numberOfDigits++; num = num / 10; } //If the number of digits are not even return "Not a Tech Number" if (numberOfDigits % 2 == 0) { num = n; //Splitting the number in two halves firstHalf = num % (int) Math.pow(10, numberOfDigits / 2); secondHalf = num / (int) Math.pow(10, numberOfDigits / 2); //calculate the sum of the square of two halves squareOfTwoHalves = (firstHalf + secondHalf) * (firstHalf + secondHalf); //compare the result with the number itself. if (n == squareOfTwoHalves) { System.out.println(n +" is a Tech number."); } else { System.out.println(n +" is not a Tech number."); } } else { System.out.println(n + " is not a Tech number."); } } }

**Output 1**: When user enters number 2025

Enter the number: 2025 2025 is a Tech number.

**Output 2**: When user enters number 1237

Enter the number: 1237 1237 is not a Tech number.

## Program to find all the Tech Numbers in a given range

Here we are writing a program to find all the tech numbers in a given range. The user enters the starting and ending range and program displays all the numbers between input ranges.

import java.util.Scanner; public class JavaExample { public static void main(String[] args) { int startRange, endRange; Scanner scan = new Scanner(System.in); System.out.print("Enter starting range: "); startRange = scan.nextInt(); System.out.print("Enter ending range: "); endRange = scan.nextInt(); scan.close(); System.out.println("All tech numbers from "+ startRange+" to "+ endRange+" are: "); /* We are looping through all the numbers in the * given range and checking whether the number is Tech * number or not, if Tech then we are displaying it. */ for(int i=startRange; i<=endRange; i++) { if (isTechNumber(i)) System.out.print(i + " "); } } //User defined function to check for Tech number private static boolean isTechNumber(int num) { int n = num; int count = 0; int firstHalf; int lastHalf; int squareOfTwoHalves; // Here we are calculating number of digits while(n != 0) { n /= 10; count++; } // If number of digits are not even return false if(count%2!=0) return false; // Splitting the number into two halves firstHalf = num / (int)Math.pow(10, count/2); lastHalf = num % (int)Math.pow(10, count/2); // calculate square of sum of two halves squareOfTwoHalves = (firstHalf + lastHalf)*(firstHalf + lastHalf); if(squareOfTwoHalves == num) return true; else return false; } }

**Output: When user enters 1 as starting range and 100 as ending range. Program displayed Tech numbers from 1 to 100.**

Enter starting range: 1 Enter ending range: 100 All tech numbers from 1 to 100 are: 81

To learn java from scratch refer my Java tutorial.

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