Fait général: 2646 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fait mathématique: 2646 is the Stirling number of the second kind S(9,6).
Culture générale: 2646 is a boring number.
Date historique: March 30th is the day in 1867 that Alaska is purchased from Russia for $7.2 million, about 2 cent/acre ($4.19/km²), by United States Secretary of State William H. Seward.