ix vs 9

ix is not a noun while 9 is a noun.

Word	Noun	Adjective	Verb	Adverb
ix	No	Yes	No	No
9	Yes	Yes	No	No

As adjectives, ix and 9 are synonyms defined as:

ix and 9: denoting a quantity consisting of one more than eight and one less than ten

Other synonyms of ix include nine.

ix (noun)	9 (noun)
	the cardinal number that is the sum of eight and one

ix (adjective)	9 (adjective)
denoting a quantity consisting of one more than eight and one less than ten	denoting a quantity consisting of one more than eight and one less than ten