These are the most common of the number codes used by the international fandom, with some explanations about how the numbers came to be.
*Information gratefully borrowed from here.
*Number codes are repeated in the character profiles.
The Japanese use TWO number systems, and both are utilized in manga/anime code names.
STANDARD counting system:
ichi, nii, san, yon/shi, go, roku, nana/shichi, hachi, kyuu/kuu, jyuu
OLD counting system:
Hi, fu, mi, yo, itsu, muu, nana, ya, kono, to
Zero (0) is sometimes read as “maru” or “rei”.
27 = 2-7 = tsu/two-na = Sawada Tsunayoshi (official)
59 = 5-9 = go-ku = Gokudera Hayato
80 = ya-ma = Yamamoto Takeshi
18 = (h)i-ba = Hibari Kyouya
69 = ro-ku (or mu-ku) = Rokudo Mukuro
96 = ku-ro = Dokuro Kuromu/Chrome
33 = sa-sa = Sasagawa Ryohei
86 = ha-ru = Miura Haru
87 = ha-na = Kurokawa Hana
56 = ko-ro = Colonello
84 = ba-shi = Basil
100 = byaku = Byakuran (“byaku” is used for counting hundreds)
51 = shou-ichi = Irie Shouichi (“shou” is used when you count by fives)
387 or 487 = su-pa-na = Spanner (Chinese 4 is “su”;Japanese will use “su” as su-ri/three)