In case you ever come across any Esperantist pirate numbers stations, the numbers are 1 unu, 2 du, 3 tri, 4 kvar, 5 kvin, 6 ses (or sis), 7 sep (or sepen), 8 ok, and 9 naŭ (sounds like «now»). It's a tossup whether they'd try to use «zéro», «nulo», «nenío», or «nul» for 0.