20776...86841 (218-digits)

This number is a prime.

                                                                    20776461
9941572864 1838619275 6236909155 1052166514 9458064414 0780736158 7978297026
9097578277 3456950091 6485895610 2503353963 5240323201 3122345135 3696598701
9759389847 7516724207 6631785858 7071472121 7992175965 5461841659 7717786841

The initial prime in the largest known prime 8-tuplet as of 2008: 330846961*503# + 349129635971 + n, for n = 0, 2, 6, 8, 12, 18, 20, 26. [Andersen]