Hecho general: 21466 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Hecho matemático: 21466 is an uninteresting number.
Trivia: 21466 is an uninteresting number.
Fecha histórica: October 8th is the day in 1856 that the Second Opium War between several western powers and China begins with the Arrow Incident on the Pearl River.