Page 486 - computer science (868) class 11
P. 486

Program 18     Write a program to input a number and using recursion method check whether the number
                               is an Emirp Number or not.
                               An emirp number is a number which is prime backwards and forwards. Example : 13 and 31
                               are both prime numbers. Thus, 13 is an emirp number.
                               class name                      :   Emirp
                               Data Members
                               int num                         :  to input a number
                               int rev                         :   stores the reverse of the number n
                               int flag                        :  is a flag variable
                               Member Methods
                               Emirp(int nn)                   :   parameterised constructor to assign num=n


                               int isprime(int x)              :    recursive function to check whether the parameter is a
                                                                 prime number or not
                               void isEmrip()                  :    calls  isprime(int)  and  checks whether it  is a emirp
                                                                 number or not

                 1       import java.util.*;

                 2       class Emirp
                 3       {
                 4           int num, rev,f;

                 5           Emirp(int nn)

                 6           {
                 7               num=nn;
                 8               rev=0;

                 9               f=2;

                10           }
                11           int isprime(int x)
                12           {

                13               if(num==x)
                14                   return 1;

                15               else if (num%x==0 || num==1)
                16                   return 0;

                17               else
                18                   return isprime(x+1);

                19           }
                20

                21           void isEmirp()
                22           {

                23               int orgnum,revnum,x;



                484484  Touchpad Computer Science-XI
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