Fatto generale: 86521 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 86521 is an uninteresting number.
Trivia: 86521 is an unremarkable number.
Data storica: November 19th is the day in 1985 that Police in Baling, Malaysia, lay siege to houses occupied by an Islamic sect of about 400 people led by Ibrahim Mahmud.