general_fact: 18 is the number of chapters into which James Joyce's epic novel Ulysses is divided.
math_fact: 18 is a heptagonal number, and as the sum of the first three pentagonal numbers, it is a pentagonal pyramidal number.
trivia: 18 is the number of levels in hell in the Chinese mythos.
historical_date: January 18th is the day in 1884 that Dr. William Price attempts to cremate the body of his infant son, Jesus Christ Price, setting a legal precedent for cremation in the United Kingdom.