2621

This number is a prime.

The largest known prime "Wilson quotient," a number of the form ((p-1)!+1)/p illustrating Wilson's theorem, is (2620!+1)/2621. It has more than 7800 decimal digits. [McCandless]

The smallest prime resulting by adding 1 to the left term of an amicable pair, i.e., (2620, 2924) [Loungrides]

The answer to "Solomon's Puzzle."

The collection of books of famous philosopher Joseph de Maistre was made of 2621 books. As usual, reference if necessary: Trénard L. (1992) La Révolution française dans la région Rhône-Alpes. Paris, Perrin, p. 658. [Olry]

There are a total of 2621 numbers which can be expressed as the product of two 2-digit numbers. Starts from 100 = 10x10, 110 = 11x10 ... and ends at 9702 = 98x99, 9801 = 99x99. [Gudipati]