digitus

Digitus, digiti is second declension masculine. Latin does not distinguish fingers from toes: digitus covers both, and when the difference matters a writer says digiti pedis. The instrumental ablative digito, "with a finger", is the form you meet most, usually with a verb of pointing or touching.

A digitus was also a unit of length, a sixteenth of a Roman foot, roughly 18mm, which is how English inherited both digit as a body part and digit as a numeral: you count on your fingers. That second meaning is the whole reason your phone is digital. Do not confuse it with dignus, "worthy", which shares nothing but a first syllable and traps beginners every year.