1129

This number is a prime.

Every date between 20th December 1423 to 21st January 1427 (inclusive) forms a composite number when the day, month and year are concatenated (20121423 to 21011427). This run of 1129 "composite dates" is the longest within 1000 years (past and future) of the present (January 2003). Note that 1129 is a prime number. [Hartley]

The smaller member in the least set of "blackjack primes," i.e., primes separated by exactly 21 consecutive composite numbers. See gaps (between primes).

The sum of the first n strong primes (n=15). [Loungrides]