Fatto generale: 83870 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 83870 is an unremarkable number.
Trivia: 83870 is an unremarkable number.
Data storica: August 17th is the day in 1980 that Azaria Chamberlain disappears, probably taken by a dingo, leading to what was then the most publicised trial in Australian history.