Hecho general: 505 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Hecho matemático: 505 is _{10}C_{5} + _{10}C_{0} + _{10}C_{5}.
Trivia: 505 is an uninteresting number.
Fecha histórica: May 19th is the day in 1997 that the Sierra Gorda Biosphere, the most ecologically diverse region in Mexico, is established as a result of grassroots efforts.