NXX
Digits four through six of a NANP number. Each NXX within an area code is assigned to a carrier and anchored to a rate center. N stands for digits 2–9, X for 0–9, so 200–999 are possible prefixes.
Digits four through six of a NANP number. Each NXX within an area code is assigned to a carrier and anchored to a rate center. N stands for digits 2–9, X for 0–9, so 200–999 are possible prefixes.