Usage notes. The numeral centum behaves like an indeclinable adjective.

What does the word centum means?

History and Etymology for centum

Latin, hundred; from the fact that its initial sound (a velar stop) is the representative of an Indo-European palatal stop — more at hundred.

What is centum used for?

A group or collection of a hundred things (especially poems, songs, etc.) or (rarely) people; a hundred.