Fatto matematico: 4398 is the number of subsets of {1, 2, 3, ... 18} that do not contain solutions to x + y = z.
Trivia: 4398 is an unremarkable number.
Data storica: January 15th is the day in 1993 that Salvatore Riina, the Mafia boss known as "The Beast", is arrested in Sicily, Italy after three decades as a fugitive.