General fact: 51643 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Mathematical fact: 51643 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Trivia: 51643 is an unremarkable number.
Historical date: May 23rd is the day in 1967 that Egypt closes the Straits of Tiran and blockades the port of Eilat at the northern end of the Gulf of Aqaba to Israeli shipping.