2137

This number is a prime.

The product of the last two digits form a number that is equal to a number formed from the first two digits of this four-digit number (21 = 3 * 7). [Avrutin]

7, 37, 137, and 2137 are prime. [Avrutin]

Number of Santa Barbara's episodes. [Avrutin]

The smallest titanic prime of the form (10^x+1)/11, where x = 2137. [Loungrides]

The next return of Halley's Comet that occurs in a prime year. [Nie]