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 an uninteresting number.
Historical date: June 23rd is the day in 1947 that the United States Senate follows the United States House of Representatives in overriding U.S. President Harry Truman's veto of the Taft-Hartley Act.