Write a program to input a number in Decimal and convert it Binary form?(9 in decimal then 1001 in binary, divide by 2)

70)  Write a program to input a number in Decimal and convert it Binary form?(9 in decimal then 1001 in binary, divide by 2)

import java.util.*;

public class Decimal_to_binary

{

    public static void main(String args[ ])

   {

           Scanner sc = new Scanner (System.in);

           System.out.println("Enter a number");

           int b = sc.nextInt();

           int a = b;

           String c = "";

           while(a>=1)

           {

               c=c+(a%2);

               a=a/2;

           }

           int k = c.length();

           System.out.print("Entered number in BINARY = ");

           for(int i = k-1;i>=0;i--)

           {

                System.out.print(c.charAt(i));

           }

   }

}

Output : 

decimal-to-binary

         Write a program to input a number and check whether it is Emirp Number (Twisted Prime) or not?(13  and its reverse 31,both are prime)