Hecho general: 9966 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Hecho matemático: 9966 is the largest 4-digit strobogrammatic number.
Trivia: 9966 is an uninteresting number.
Fecha histórica: April 14th is the day in 2005 that the Oregon Supreme Court nullifies marriage licenses issued to gay couples a year earlier by Multnomah County.