invariant vs changeless

invariant is a noun but changeless is not a noun.

Word	Noun	Adjective	Verb	Adverb
invariant	Yes	Yes	No	No
changeless	No	Yes	No	No

As adjectives, invariant and changeless are synonyms defined as:

Other synonyms of invariant include constant, unvarying.

invariant (noun)	changeless (noun)
a feature (quantity or property or function) that remains unchanged when a particular transformation is applied to it

invariant (adjective)	changeless (adjective)
unvarying in nature	not subject or susceptible to change or variation in form or quality or nature
unaffected by a designated operation or transformation	unvarying in nature
	remaining the same for indefinitely long times