Hecho general: 420 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Hecho matemático: 420 is the smallest number divisible by 1 through 7.
Trivia: 420 is a boring number.
Fecha histórica: February 23rd is the day in 1943 that a fire breaks out at St. Joseph's Orphanage, County Cavan, Ireland, killing 36 people (35 of whom are children).