one - ichi, ikko, bou, hitotsu, wan, issun
two - ni, futatsu
three - san, mittsu, mi
four - yon, yottsu, shi
five - go, itsutsu
six - roku, muttsu, mu, mutsu
seven - shichi, sebun, nanatsu
eight - hatsu, hachi, yattsu, eito, yatsu, ya
nine - kokonotsu, kyuu, ku, nain
ten - juu, to, too
10 - 19: juu + "1-9" eg: 11 = juuichi
same theory apply to 10 - 99
hundred: hyaku
thousand: chi, ikusen
參考: My Japanese Class