Fatto matematico: 2120 is the number of ways to stack 16 pennies in a line so that each penny lies on the table or on two pennies.
Trivia: 2120 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Data storica: October 20th is the day in 1904 that Chile and Bolivia sign the Treaty of Peace and Friendship, delimiting the border between the two countries.