Fatto generale: 21673 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 21673 is an uninteresting number.
Trivia: 21673 is an unremarkable number.
Data storica: May 3rd is the day in 2001 that the United States loses its seat on the U.N. Human Rights Commission for the first time since the commission was formed in 1947.