Fatto matematico: 2820 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Trivia: 2820 is a boring number.
Data storica: September 20th is the day in 2008 that a dump truck full of explosives detonates in front of the Marriott hotel in Islamabad, Pakistan, killing 54 people and injuring 266 others.