Fatto generale: 5773 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 5773 is the index of a triangular number containing only 3 different digits.
Trivia: 5773 is an unremarkable number.
Data storica: October 21st is the day in 1959 that President Dwight D. Eisenhower signs an executive order transferring Wernher von Braun and other German scientists from the United States Army to NASA.