Hecho general: 4524 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Hecho matemático: 4524 is the maximum number of pieces a torus can be cut into with 29 cuts.
Trivia: 4524 is a boring number.
Fecha histórica: May 20th is the day in 1609 that Shakespeare's sonnets are first published in London, perhaps illicitly, by the publisher Thomas Thorpe.