21683...12081 (238-digits)

This number is a probable-prime (likely to be a prime but we have not (re-)proven it on this site).

                                              21683598 9920396714 1909859571
4931036846 9343237759 3540860949 8414494483 6600031574 2149036132 0830986782
8161416147 0603332440 9989874914 4305554915 0653734649 0399034396 5963643427
4450898558 0100420550 0513549828 3137655596 6346270248 4559944779 8331212081

The smallest multidigit prime of the form 6ⁿ + n. [Gudipati]