809
This number is a prime.
Formerly the area code for the entire Caribbean. According to the National Fraud Information Center, it has been associated with long distance phone scams.
The only three-digit circular-digit prime.
The hotel room number in the 1952 film Don't Bother to Knock, starring Richard Widmark and Marilyn Monroe. Marilyn's character (Nell Forbes) is a lonely blonde who has recently been released from a mental institution. [McCranie]
The smallest prime whose fourth power is zeroless pandigital (i.e., containing all digits from 1 to 9). [Gupta]
The largest prime less than 10000 such that 2p-F(p) is also prime, where F(p) is the pth Fibonacci number. [Opao]
The lesser of the smallest twin prime pair that contain no prime digits. [Punches]
The smallest circular-digit Cyclops prime. [Punches]
809 is the start of 21 consecutive primes which alternate between the forms 6n - 1 and 6n + 1. The smallest start of 22 such primes is the much larger 3954889. [Andersen]
Largest known prime p such that T(p) is prime in Juricevic
conjecture on classification of Lehmer triples. Juricevic
conjectured an infinite number of such primes. Yu Tsumura
proved that T(p) is infinitely often composite. [Post]
The larger of only two 3-digit distinct-digit primes whose
the absolute difference between any two of its digits is a
non-prime number. The other is 109. [Loungrides]