When spelling numbers from 1 to 100 (One, Two, Three... Ninety-nine, One hundred), none of them contain the letter 'A'. The letter 'A' first appears in 'Thousand'.
This is a fun quirk of English number spellings: none of the words for 1 through 100 — one, two, three, ... twenty, thirty, ... ninety, hundred — contain the letter a. It's a classic trick trivia fact people don't notice until they check. The first number that does contain an a is actually "thousand".