Fatto generale: 21628 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 21628 is a boring number.
Trivia: 21628 is an uninteresting number.
Data storica: March 19th is the day in 1687 that Explorer Robert Cavelier de La Salle, searching for the mouth of the Mississippi River, is murdered by his own men.