Java: Check if a number is Mersenne number or not

Last update on May 15 2025 13:10:04 (UTC/GMT +8 hours)

Check 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

Pictorial Presentation:

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. 

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to check if a number is a Mersenne number by verifying if it can be written as 2^n - 1 using bitwise operations.
• Write a Java program to generate Mersenne numbers up to a given limit and check each for primality.
• Write a Java program to determine the value of n for which a given number equals 2^n - 1 using logarithms.
• Write a Java program to compare a given number with the nearest Mersenne number by computing powers of 2 iteratively.

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