i vs 1

i and 1 both are nouns.

Word	Noun	Adjective	Verb	Adverb
i	Yes	Yes	No	No
1	Yes	Yes	No	No

As adjectives, i and 1 are synonyms defined as:

Other synonyms of i include ane, one.

i (noun)	1 (noun)
the 9th letter of the Roman alphabet	the smallest whole number or a numeral representing this number

i (adjective)	1 (adjective)
used of a single unit or thing; not two or more	used of a single unit or thing; not two or more