General fact: 540 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Mathematical fact: 540 is divisible by its reverse.
Trivia: 540 is a boring number.
Historical date: June 23rd is the day in 1985 that a terrorist bomb aboard Air India flight 182 brings the Boeing 747 down off the coast of Ireland killing all 329 aboard.