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What is the North American Numbering Plan?

The North American Numbering Plan, known as NANP, is the integrated telephone numbering system serving 19 North American countries that share its resources. These countries include the United States and its territories, Canada, Bermuda, Anguilla, Antigua & Barbuda, the Bahamas, Barbados, the British Virgin Islands, the Cayman Islands, Dominica, the Dominican Republic, Grenada, Jamaica, Montserrat, St. Kitts and Nevis, St. Lucia, St. Vincent and the Grenadines, Trinidad and Tobago, and Turks & Caicos.

What are NPA NXX codes?

NANP numbers are ten-digit numbers consisting of a three-digit Numbering Plan Area (NPA) code, commonly called an area code, followed by a seven-digit local number. The local number consists of a three-digit prefix, exchange (NXX) code followed by a four-digit station number. NPA NXX codes are also known as Central Office Codes. The format is usually represented as

NXX-NXX-XXXX

where N is any digit from 2 through 9 and X is any digit from 0 through 9. Thus an NPA NXX code is the first six digits of any North American telephone number.

How are NPA NXX codes assigned?

NPA NXX codes are assigned by rate center and can either be issued in ten thousand blocks (NPA NXX) or thousand blocks (NPA NXX X). Thousand blocks are only issued in number pooling areas, while ten thousand blocks are only issued in non-pooling areas or under certain circumstances in pooling areas.