X vs large integer

X and large integer both are nouns.

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

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

X: the cardinal number that is the sum of nine and one; the base of the decimal system
large integer: an integer equal to or greater than ten

X (noun)	large integer (noun)
street names for methylenedioxymethamphetamine	an integer equal to or greater than ten
the 24th letter of the Roman alphabet
the cardinal number that is the sum of nine and one; the base of the decimal system