math_fact: 6111 is a value of n for which s(n-1) = s(n+1).
trivia: 6111 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
historical_date: September 23rd is the day in 1641 that the Merchant Royal, carrying a treasure worth over a billion US dollars, is lost at sea off Land's End.