277777788888989

This number is a prime.

                                                            27777 7788888989

The smallest prime with a multiplicative persistence (i.e., the number of times the digit product must be iterated in order to reach a single-digit product) of 11: 277777788888989 --> 4996238671872 --> 438939648 --> 4478976 --> 338688 --> 27648 --> 2688 --> 768 --> 336 --> 54 --> 20 --> 0. [Beedassy]