Java Program to Check Automorphic Number

Last Updated: 14 March, 2023

On this tutorial page we are going to learn how to write a Java program to check whether number is automorphic or not.

An automorphic number is a number which is present in the last digit(s) of its square. In other words, an automorphic number is a number "n" such that "n^2" ends with "n".

For example, 5 is an automorphic number, since 5^2 = 25 and the last digit of 25 is 5. Similarly, 25 is also an automorphic number, since 25^2 = 625 and the last two digits of 625 are 25.

Here's a Java program to check if a given number is an automorphic number:

Example 1: Check number is Automorphic or not in Java

  public class AutomorphicNumberExample1 {
    static void checkAutomorphicNumber(int number) {
      int num = number;
      // finding square value of the given number
      int squareNum = num * num;
      
      // iterating and comparing the num value until it becomes 0
      while (num > 0) {
        // Comparing remainder value of num and squareNum  
        if (num % 10 != squareNum % 10) {
          // returning false if both values are not equal
          System.out.println(number + " is not an Automorphic Number.");
          return;
        }
  
        num = num / 10;
        squareNum = squareNum / 10;
      }
      
      System.out.println(number + " is an Automorphic Number.");
    }
  
    public static void main(String args[]) {
      checkAutomorphicNumber(76);
      checkAutomorphicNumber(125);
    }
  }

Output

76 is an Automorphic Number.
125 is not an Automorphic Number.

Example 2: Check number is Automorphic or not using Scanner Class

  
  import java.util.Scanner;
  public class AutomorphicNumberExample2 {
    public static void main(String args[]) {
      int num, sqrNum, temp, sqrNumRemainder, c = 0;
      
      Scanner scanner = new Scanner(System.in);
      System.out.print("Enter the number: ");
      num = scanner.nextInt();
      scanner.close();
      temp = num;
      while (temp > 0) {
        temp = temp / 10;
        c++;
      }
      sqrNum = num * num;
      sqrNumRemainder = sqrNum % (int) Math.pow(10, c);
      if (sqrNumRemainder == num) {
        System.out.println("Yes, It's an Automorphic Number.");
      } else {
        System.out.println("Not, It's not an Automorphic Number");
      }
    }
  }

Output 1

Enter the number: 85
Not, It's not an Automorphic Number

Output 2

Enter the number: 625
Yes, It's an Automorphic Number.

Example 3: Print Automorphic Numbers between two numbers

  
  import java.util.Scanner;
  public class AutomorphicNumberExample3 {
    private static boolean isAutomorphic(int num) {
      int count = 0;
      int square = num * num;
      int temp = num;
      while (temp > 0) {
        count++;
        temp = temp / 10;
      }
      int lastDigit = (int) (square % (Math.pow(10, count)));
      return num == lastDigit;
    }
    
    public static void main(String args[]) {
      Scanner scanner = new Scanner(System.in);
      int startNum, endNum;
      System.out.println("Print Automorphic Numbers between two different numbers");
      System.out.print("Enter the starting number: ");
      startNum = scanner.nextInt();
      System.out.print("Enter the ending number: ");
      endNum = scanner.nextInt();
      scanner.close();
      
      System.out.println("\nAutomorphic numbers between " + startNum + " and " + endNum + " are: ");
      
      for (int num = startNum; num <= endNum; num++) {
        if (isAutomorphic(num))
          System.out.print(num + " ");
      }
    }
  }

Output

Print Automorphic Numbers between two different numbers
Enter the starting number: 10
Enter the ending number: 1000

Automorphic numbers between 10 and 1000 are: 
25 76 376 625