Fatto matematico: 1787 is the number of different arrangements (up to rotation and reflection) of 12 non-attacking queens on a 12×12 chessboard.
Trivia: 1787 is an unremarkable number.
Data storica: November 21st is the day in 1905 that Albert Einstein's paper, Does the Inertia of a Body Depend Upon Its Energy Content?, is published in the journal "Annalen der Physik".