on the whole vs altogether

on the whole is not a noun while altogether is a noun.

Word	Noun	Adjective	Verb	Adverb
on the whole	No	No	No	Yes
altogether	Yes	No	No	Yes

As adverbs, on the whole and altogether are synonyms defined as:

on the whole and altogether: with everything considered (and neglecting details)

Other synonyms of on the whole include all in all, tout ensemble.

on the whole (noun)	altogether (noun)
	informal terms for nakedness

on the whole (adverb)	altogether (adverb)
with everything considered (and neglecting details)	with everything included or counted
	with everything considered (and neglecting details)
	to a complete degree or to the full or entire extent; Completely or entirely