Fatto generale: 21173 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 21173 is an uninteresting number.
Trivia: 21173 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Data storica: December 19th is the day in 1776 that Thomas Paine publishes one of a series of pamphlets in the Pennsylvania Journal titled The American Crisis.