Problem: Write a Java program to check whether the given number is Twisted Prime or not.

A number is said to be Twisted Prime if it is a prime number and its reverse is also a prime number.

Example:

Twisted Prime

Steps to check Twisted Prime in Java:

  1. Input a number.
  2. Check if the number is prime.
  3. If the number is prime, compute its reverse.
  4. Check if the reverse is prime.
  5. If both step-2 and step-4 are true, then the input number is Twisted Prime, else not.

Here is the implementation of the steps in Java:

import java.util.Scanner;

class Main {
  public static void main(String[] args) {
    Scanner in=new Scanner(System.in);
    System.out.print("Enter a number: ");
    int n=in.nextInt();

    if(isPrime(n)){

      //Computing Reverse
      int rev=0;
      while(n>0){
        rev=rev*10 + n%10;
        n=n/10;
      }

      if(isPrime(rev))
        System.out.println("Twisted Prime");
      else
        System.out.println("Not a Twisted Prime");
    }
    else
        System.out.println("Not a Twisted Prime");
    
  }

  //Function to Check Prime Number
  private static boolean isPrime(int n){
    for(int i=2; i<(n/2); i++){
      if(n%i==0)
        return false;
    }
    return true;
  }
}

Output:

Enter a number: 31
Twisted Prime


In the above program, the isPrime(int n) function returns true if the passed number (i.e. n) is a prime number, otherwise it returns false.

We use the isPrime(int n) to check whether the input and its reverse are prime or not.

If anyone of them is not a prime number then it means input is not a Twisted Prime.

If both the numbers are prime then the input is said to be a Twisted Prime number.

In this programming example, we learned to check Twisted Prime number in Java programming language.

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