2 vs digit

2 and digit both are nouns.

Word	Noun	Adjective	Verb	Adverb
2	Yes	Yes	No	No
digit	Yes	No	No	No

As nouns, digit is a hypernym of 2; that is, digit is a word with a broader meaning than 2:

2: the cardinal number that is the sum of one and one or a numeral representing this number
digit: one of the elements that collectively form a system of numeration

Other hypernyms of 2 include figure.

2 (noun)	digit (noun)
the cardinal number that is the sum of one and one or a numeral representing this number	a finger or toe in human beings or corresponding body part in other vertebrates
	one of the elements that collectively form a system of numeration
	the length of breadth of a finger used as a linear measure

2 (adjective)	digit (adjective)
being one more than one