Quindecimal (alternatively called Pentadecimal) is a number base with 15 digits. It's similar to Duodecimal (12 digits) or Vigesimal (20 digits). Oh, and if you're wondering why numbers like 10 and 11 are called "quen" and "elefen" instead of "ten" and "eleven", it's because those are my base-15 names for them. Also, 9 is different to avoid inflation. 12 isn't different because it is NOT cannibalism (the numbers aren't even sentient).
Credit 2 Every1, especially @AlexFar3101 for the Number Elimination vectors, Nintendo for the stomp sound, @Math506 (banned) for the safe, @mahhi-train for the 18 idea, and Sesame Street for Number Elimination and Cookie Monster.