Number Format of the North American Numbering Plan
Number format: NPA-NXX-xxxx
NPA - Numbering Plan Area Code. Covers Canada, the United States, parts of the Caribbean Sea, and some Atlantic and Pacific islands. The area code is often enclosed in parentheses.
NXX - Central Office (exchange) code. Often considered part of a subscriber number. The three-digit Central Office codes are assigned to a specific CO serving its customers, but may be physically dispersed by redirection, or forwarding to mobile operators and other services.
xxxx - Subscriber Number. This unique four-digit number is the subscriber number or station code.
The North American Numbering Plan (NANP) is an integrated telephone numbering plan that encompasses 25 countries and territories primarily in North America, the Caribbean, and U.S. territories. However, not all North American countries participate in the NANP.
The NANP is a system of numbering plan areas (NPA) using telephone numbers consisting of a three-digit area code, a three-digit central office code, and a four-digit station number. Through this plan, telephone calls can be directed to particular regions of the larger NANP public switched telephone network (PSTN), where they are further routed by the local networks. The NANP is administered by the North American Numbering Plan Administration (NANPA), a service operated by Neustar Inc. The international calling code for the NANP is 1.