12345...67891 (28-digits)

This number is a prime.

                                              12345678 9123456789 1234567891

One of the primes in the Smarandache deconstructive sequence of integers, which is constructed by sequentially repeating the digits (from 1 to 9) in the following way: 1, 23, 456, 7891, 23456, 789123, 4567891, 23456789, 123456789, 1234567891, ....