Area Code 634 – Sonora

Geographic Coverage and Jurisdiction

The +52 634 area code is a geographic National Destination Code (NDC) assigned to the northern part of the state of Sonora, Mexico. It covers the municipalities of Agua Prieta, Cananea, Naco, and adjacent rural localities, along the U.S.–Mexico border. Administratively, these areas fall under the jurisdiction of the Federal Telecommunications Institute (IFT) and are served by local exchange carriers operating within the PSTN. The region is characterized by mining, cross-border trade, and agricultural activity, with Agua Prieta serving as a major border crossing to Douglas, Arizona.

Primary Cities and Local Dialing

Key population centers within this code include Agua Prieta, Cananea, and Naco. For local calls within the same area code, users in Mexico typically dial only the seven-digit local number (e.g., 123-4567). However, due to the North American Numbering Plan influence in border regions, some local exchanges may require 10-digit dialing for calls between different central offices within the same NDC. Always confirm with your local service provider.

International Dialing Format

To call a number in the 634 area code from abroad, you must use Mexico's country code +52, followed by the area code and the seven-digit subscriber number. The complete international format is: +52 634 XXX XXXX. For example, a landline in Agua Prieta might be dialed as +52 634 123 4567 from the United States or any other country. When dialing from a mobile phone, replace the international access code (e.g., 011 from the U.S.) with the plus sign.

Overlay and Numbering Considerations

As of the latest IFT updates, the 634 area code does not have an overlay code; it is the sole geographic code for this region. However, number exhaustion is a consideration, and the IFT may introduce an overlay in the future. If an overlay is implemented, 10-digit dialing would become mandatory for all local calls. For now, local calls within the same area code can often be completed using seven digits, but for calls from other area codes in Mexico, you must dial the full national long-distance prefix (01) followed by the area code and number: 01 634 XXX XXXX.

Caller Instructions

For local callers within the 634 area code: If you are calling a number in the same city, dial the seven-digit local number. If you are calling from a different city within the same area code, you may need to dial the area code first, depending on your carrier's setup. For callers from other parts of Mexico: Dial 01 (national long-distance prefix) + 634 + the seven-digit number. For international callers: Dial your country's exit code (e.g., 00 from most European countries, 011 from the U.S./Canada), then 52, then 634, then the seven-digit number. Alternatively, use +52 634 XXX XXXX on mobile devices.

This area code is used exclusively for fixed-line services; mobile numbers in the same region are assigned to non-geographic mobile prefixes (e.g., 634 is not used for mobiles). If you receive a call from +52 634, it originates from a landline in northern Sonora.