twenty-two vs xxii

twenty-two is a noun but xxii is not a noun.

Word	Noun	Adjective	Verb	Adverb
twenty-two	Yes	Yes	No	No
xxii	No	Yes	No	No

As adjectives, twenty-two and xxii are synonyms defined as:

Other synonyms of twenty-two include 22.

twenty-two (noun)	xxii (noun)
a .22 caliber firearm (pistol or rifle)
the cardinal number that is the sum of twenty-one and one

twenty-two (adjective)	xxii (adjective)
being two more than twenty	being two more than twenty