64th vs sixty-fourth

64th is not a noun while sixty-fourth is a noun.

Word	Noun	Adjective	Verb	Adverb
64th	No	Yes	No	No
sixty-fourth	Yes	Yes	No	No

As adjectives, 64th and sixty-fourth are synonyms defined as:

64th and sixty-fourth: the ordinal number of sixty-four in counting order

64th (noun)	sixty-fourth (noun)
	one part in sixty-four equal parts

64th (adjective)	sixty-fourth (adjective)
the ordinal number of sixty-four in counting order	the ordinal number of sixty-four in counting order