immutableness vs immutability

immutableness and immutability both are nouns.

Word	Noun	Adjective	Verb	Adverb
immutableness	Yes	No	No	No
immutability	Yes	No	No	No

As nouns, immutableness and immutability are synonyms defined as:

immutableness and immutability: the quality of being incapable of mutation

Other synonyms of immutableness include fixity.

immutableness (noun)	immutability (noun)
the quality of being incapable of mutation	the quality of being incapable of mutation