1663

This number is a prime.

A prime p such that 4p + 7 is prime. [Russo]

The smallest prime number for which the sum of the reciprocals of its digits equals the sum of the reciprocals of the digits of its prime index (261). [Gaydos]

PO Box 1663, Santa Fe, New Mexico, was the sole mailing address for the top-secret Los Alamos Laboratory during World War II. [Harrison]

1663 is the 666th positive integer that ends with a prime digit. [Gaydos]

London's oldest theatre, Theatre Royal Drury Lane, has stood at the location since 1663. [Harrison]