41996139943

This number is a prime.

                                                                4 1996139943

                    3419961399433
                   334199613994333 
                  33341996139943333
                 3333419961399433333
                333334199613994333333
                999994199613994399999
                 9999419961399439999
                  99941996139943999   
                   994199613994399
                    9419961399439

Each of the above ten numbers is prime. 41996139943 is the smallest prime with this property. [Firoozbakht]