Fatto generale: 4311 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 4311 is the largest number n known with the property that n-2^{k} is a pseudoprime for all k>0.
Trivia: 4311 is a boring number.
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.