Hecho general: 21618 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Hecho matemático: 21618 is an unremarkable number.
Trivia: 21618 is an unremarkable number.
Fecha histórica: March 9th is the day in 1566 that David Rizzio, private secretary to Mary, Queen of Scots, is murdered in the Palace of Holyroodhouse, Edinburgh, Scotland.