one thousand thousand vs million

one thousand thousand and million both are nouns.

Word	Noun	Adjective	Verb	Adverb
one thousand thousand	Yes	No	No	No
million	Yes	Yes	No	No

As nouns, one thousand thousand and million are synonyms defined as:

one thousand thousand and million: the number that is represented as a one followed by 6 zeros

Other synonyms of one thousand thousand include 1000000, meg.

one thousand thousand (noun)	million (noun)
the number that is represented as a one followed by 6 zeros	the number that is represented as a one followed by 6 zeros
	a very large indefinite number (usually hyperbole)

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