at least vs at the least

at least and at the least both are adverbs.

Word	Noun	Adjective	Verb	Adverb
at least	No	No	No	Yes
at the least	No	No	No	Yes

As adverbs, at least and at the least are synonyms defined as:

at least (adverb)	at the least (adverb)
not less than	not less than
if nothing else (`leastwise' is informal and `leastways' is colloquial)