10252...56287 (26-digits)

This number is a prime.

                                                102522 5669329856 1414756287

As of October 2004, this prime starts the largest known 16-tuplet:
10252256693298561414756287 + 0, 2, 6, 12, 14, 20, 26, 30, 32, 36, 42, 44, 50, 54, 56, 60. [Andersen]