Fait mathématique: 9643 is the smallest number that can not be formed using the numbers 2^{0}, 2^{1}, ... , 2^{7}, together with the symbols +, –, × and ÷.
Culture générale: 9643 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Date historique: May 26th is the day in 1970 that the Soviet Tupolev Tu-144 becomes the first commercial transport to exceed Mach 2.