Mersenne Number

 

Write a program to check if a number is a Mersenne number or not.

In  mathematics, a Mersenne number is a number that can be written in the form M(n) = 2ⁿ − 1 for some integer n.
The first four Mersenne primes are 3, 7, 31, and 127

Test Data
Input a number: 127

Sample Solution:

Java Code:

import java.util.Scanner;
import java.math.BigInteger;
public class Example22 {

    public static void main(String args[])
    {
        Scanner in = new Scanner(System.in);
        System.out.print("Input a number: ");
        int n = in.nextInt();
        int n1 = n + 1;

        int power = 0;
        int ans = 0;
        for(int i=0;;i++)
        {
            power=(int)Math.pow(2,i);
            if(power>n1)
            {
                break;
            }
            else if(power==n1)
            {
               System.out.println(n+" is a Mersenne number.");
               ans=1;
            }
        }
  if(ans==0)
  {
   System.out.println(n+" is not a Mersenne number.");
  }
    }
}

Sample Output:

Input a number: 127                                                                                           
127 is a Mersenne number.