utmost vs farthermost

utmost is a noun but farthermost is not a noun.

Word	Noun	Adjective	Verb	Adverb
utmost	Yes	Yes	No	No
farthermost	No	Yes	No	No

As adjectives, utmost and farthermost are synonyms defined as:

utmost and farthermost: (comparatives of `far') most remote in space or time or order

Other synonyms of utmost include farthest, furthermost, furthest, uttermost.

utmost (noun)	farthermost (noun)
the greatest possible degree

utmost (adjective)	farthermost (adjective)
(comparatives of `far') most remote in space or time or order	(comparatives of `far') most remote in space or time or order
of the greatest possible degree or extent or intensity