Fait général: 1573 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fait mathématique: 1573 is a value of n for which n, 2n, 3n, and 4n all use the same number of digits in Roman numerals.
Culture générale: 1573 is an unremarkable number.
Date historique: April 21st is the day in 1894 that Norway formally adopts the Krag-Jørgensen rifle as the main arm of its armed forces, a weapon that would remain in service for almost 50 years.