math_fact: 8669 is the maximum value of n so that there exist 5 denominations of stamps so that every postage from 1 to n can be paid for with at most 18 stamps.
trivia: 8669 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
historical_date: September 25th is the day in 1868 that the Imperial Russian steam frigate Alexander Neuski is shipwrecked off Jutland while carrying Grand Duke Alexei of Russia.