Hecho general: 326 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Hecho matemático: 326 is the number of permutations of some subset of 5 elements.
Trivia: 326 is a boring number.
Fecha histórica: 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".