Fatto generale: 5543 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 5543 is an uninteresting number.
Trivia: 5543 is a boring number.
Data storica: March 5th is the day in 1981 that the ZX81, a pioneering British home computer, is launched by Sinclair Research and would go on to sell over 1.5 million units around the world.