Fatto generale: 6598 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 6598 is a boring number.
Trivia: 6598 is a boring number.
Data storica: January 23rd is the day in 1510 that Henry VIII of England, then 18 years old, appears incognito in the lists at Richmond, and is applauded for his jousting before he reveals his identity.