66666...77777 (2131-digits)

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

A curious Fermat and Lucas PRP made up of 6s, 7s, and the number 37818 in the center. Note that if you enter 37818 into a calculator, then turn the calculator upside down, it looks as if the word 'BIBLE' is spelled. [Earls]