Fatto matematico: 819 is the smallest number so that it and its successor are both the product of 2 primes and the square of a prime.
Trivia: 819 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Data storica: March 29th is the day in 1961 that the Twenty-third Amendment to the United States Constitution is ratified, allowing residents of Washington, D.C., to vote in presidential elections.