99799...77821 (81-digits)

This number is a prime.

                                                                9 9799198381
1983709971 8594437096 4191985782 9593757839 6913598839 2933797757 7239877821

The largest prime formed from twenty-seven 3-digit primes such that deleting one 3-digit prime from the right each time remains prime. [Gaydos]