Kotlin: Reverse a Number

1. Introduction

Reversing a number means presenting its digits in the opposite order. For instance, reversing the number 12345 would yield 54321. Such operations are not only academic exercises but also find practical applications in algorithm development and problem-solving. In this post, we'll dive into a Kotlin-based approach to reverse a number.

2. Program Overview

Our Kotlin program will:

1. Take a numerical input from the user.

2. Break the number down into its digits and rearrange them in reverse order.

3. Present the reversed number to the user.

3. Code Program

import java.util.Scanner

fun main() {
    // Incorporate Scanner for user input
    val reader = Scanner(System.in)

    // Request the user for a number
    print("Enter a number: ")
    var num = reader.nextInt()

    var reversedNumber = 0

    // Process to reverse the number
    while (num != 0) {
        val digit = num % 10
        reversedNumber = reversedNumber * 10 + digit
        num /= 10

    // Display the reversed number
    println("Reversed Number: $reversedNumber")


Enter a number: 12345
Reversed Number: 54321

4. Step By Step Explanation

1. Scanner Setup: We begin by initiating the Scanner class, which enables us to fetch user input. We've labeled our instance reader.

2. Number Collection: The user provides a number, which will subsequently be reversed.

3. Reversal Mechanism: To reverse the number:

  • We initiate a loop that continues as long as the given number isn't zero.
  • Within each loop iteration, we obtain the last digit of the number using the modulus operator %. This digit is then added to our reversedNumber after shifting its current value to the left (multiplying by 10). We then truncate the last digit from the original number by dividing it by 10.
  • This cycle is reiterated until the entire number has been reversed.

4. Outcome Display: Upon successful reversal, the reversedNumber is presented to the user via the println function.

Through this Kotlin illustration, we navigate a fundamental numerical manipulation, deepening our understanding of loops and arithmetic operations. Such tasks underline Kotlin's utility in algorithmic problem-solving.