121312141213121

This number is a prime.

                                                            12131 2141213121

Just showing those entries submitted by 'Lovelace': (Click here to show all)

The smallest palindromic prime with its decimal digits following the ABACABA sequence (start with 1 and for each next term, first take the previous term, add the next unused digit, and then repeat the previous term.) [Lovelace]