Hecho general: 5599 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Hecho matemático: 5599 is an unremarkable number.
Trivia: 5599 is an uninteresting number.
Fecha histórica: April 30th is the day in 1863 that a 65-man French Foreign Legion infantry patrol fought a force of nearly 2,000 Mexican soldiers to nearly the last man in Hacienda Camarón, Mexico.