There are four Kanjis.
Meanings:
9 | 10
100|1000
Readings:
9: kyû, ku, kokono, kokonotsu
10: jû, ji, tô, to
100: hyaku
1000: sen

Interesting fact: In Japanese you say each digit and their "place". E.g.: 9999 is read "kyû sen kyû hyaku kyû jû kyû" (literally "9 thousand 9 hundred 9 ten 9").