九百(きゅうひゃく)

九(きゅう) + 百(ひゃく). Both parts keep their normal shape.

Pronunciation

Always きゅうひゃく, never くひゃく. The く reading of 九(きゅう) survives only in fixed words such as 九月(くがつ) (September) and 九時(くじ) (nine o'clock).

Sound changes in the hundreds

Only 三百(さんびゃく), 六百(ろっぴゃく), and 八百(はっぴゃく) change; 九百(きゅうひゃく) and the rest are regular.