digit vs whole number

digit and whole number both are nouns.

Word	Noun	Adjective	Verb	Adverb
digit	Yes	No	No	No
whole number	Yes	No	No	No

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

Other hypernyms of digit include integer.

digit (noun)	whole number (noun)
a finger or toe in human beings or corresponding body part in other vertebrates	any of the natural numbers (positive or negative) or zero
one of the elements that collectively form a system of numeration
the length of breadth of a finger used as a linear measure