General fact: 4133 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Mathematical fact: 4133 is an unremarkable number.
Trivia: 4133 is an unremarkable number.
Historical date: April 25th is the day in 1134 that the name Zagreb was mentioned for the first time in the Felician Charter relating to the establishment of the Zagreb Bishopric around 1094.