million vs large integer

million and large integer both are nouns.

Word	Noun	Adjective	Verb	Adverb
million	Yes	Yes	No	No
large integer	Yes	No	No	No

As nouns, large integer is a hypernym of million; that is, large integer is a word with a broader meaning than million:

million (noun)	large integer (noun)
the number that is represented as a one followed by 6 zeros	an integer equal to or greater than ten
a very large indefinite number (usually hyperbole)

million (adjective)	large integer (adjective)
(in Roman numerals, M written with a macron over it) denoting a quantity consisting of 1,000,000 items or units