Hecho matemático: 5499 is the average of all the even 4-digit numbers.
Trivia: 5499 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fecha histórica: January 20th is the day in 1972 that Pakistan launched its Nuclear detterent program few weeks after its defeat in Bangladesh Liberation War and Indo-Pakistani War of 1971.