Fatto generale: 1903 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 1903 is the smallest number requiring an addition chain of length 15.
Trivia: 1903 is an unremarkable number.
Data storica: March 17th is the day in 1948 that Benelux, France, and the United Kingdom sign the Treaty of Brussels, a precursor to the North Atlantic Treaty establishing NATO.