Fatto generale: 21170 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 21170 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Trivia: 21170 is a boring number.
Data storica: December 16th is the day in 1811 that the first two in a series of four severe earthquakes occur in the vicinity of New Madrid, Missouri.