Hecho matemático: 9643 is the smallest number that can not be formed using the numbers 2^{0}, 2^{1}, ... , 2^{7}, together with the symbols +, –, × and ÷.
Trivia: 9643 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fecha histórica: May 26th is the day in 1135 that Alfonso VII of León and Castile is crowned in the Cathedral of Leon as Imperator totius Hispaniae, "Emperor of all of Spain".