19999...99999 (402-digits)

This number is a prime.

2*10⁴⁰¹-1 is a 'near-repdigit' prime; all digits except the lead one are the same. When Samuel Yates first started maintaining his list of the largest known primes in 1979, this number was the 49th largest of the 50 known primes of over 400 digits. [Dobb]