four-hundredth vs ordinal

four-hundredth is not a noun while ordinal is a noun.

Word	Noun	Adjective	Verb	Adverb
four-hundredth	No	Yes	No	No
ordinal	Yes	Yes	No	No

four-hundredth (noun)	ordinal (noun)
	the number designating place in an ordered sequence

four-hundredth (adjective)	ordinal (adjective)
the ordinal number of four hundred in counting order	being or denoting a numerical order in a series
	of or relating to a taxonomic order