Hecho matemático: 21749 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Trivia: 21749 is an uninteresting number.
Fecha histórica: July 18th is the day in 1857 that Louis Faidherbe, French governor of Senegal, arrives to relieve French forces at Kayes, effectively ending El Hajj Umar Tall's war against the French.