Fatto matematico: 1621 is a prime that remains prime when preceded and followed by one, two, three, or four 3's.
Trivia: 1621 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Data storica: June 8th is the day in 1887 that Herman Hollerith applies for US patent #395,791 for the 'Art of Applying Statistics' – his punched card calculator.