The search for the 521 area code is complicated because the number sequence has two distinct meanings in the world of telecommunications, neither of which is a traditional geographic location like a U.S. state or Canadian province.
- North American Numbering Plan (NANP): 521 is a Non-Geographic Area Code (NGPA) used for specialized services in the US and Canada.
- Mexico Dialing: The sequence 52 1 historically served as the dialing prefix for Mexican mobile phones when calling internationally.
This article clarifies both uses, details the Mexican dialing changes, and explains why you might encounter a 521 number.
- 521 in the North American Numbering Plan (NANP)
In the United States and Canada, the 521 area code has been assigned by the NANPA, but not to a physical location.
| Detail | Information |
| Area Code Status: | Assigned (Since 2017) |
| Location: | Non-Geographic Services |
| Primary Use: | Reserved for services that are not tied to a specific city or region, similar to 500. This is typically for specialized telecom routing, testing, or network services. |
| Time Zone: | None. As it is non-geographic, it does not adhere to a time zone. |
Numbers assigned to the 521 code are generally used by large corporations or service providers for internal purposes and are not usually encountered by the public. However, if a call displays a 521 area code, it is being routed through a specialized network.
- The Historical “52 1” Mobile Dialing Prefix (Mexico)
Historically, the sequence +52 1 was the crucial dialing pattern for reaching mobile phones in Mexico from abroad.
What the Numbers Mean:
- +52: The official Country Calling Code for Mexico.
- 1: This digit, historically mandated by Mexican regulators, had to be inserted between the country code (52) and the Mexican mobile number when dialing from outside of Mexico.
Important Change: The Removal of the ‘1’
In August 2020, Mexico formally eliminated the required insertion of the “1” for all international calls to Mexican mobile numbers.
| Type of Number | Old International Format (Pre-Aug 2020) | New International Format (Current) |
| Landline | +52+Area Code+Local Number | +52+Area Code+Local Number |
| Mobile | +52+1+10-Digit Mobile Number | +52+10-Digit Mobile Number |
If you see a full 10-digit number preceded by +52 1, it is an outdated format for a Mexican mobile number. The current correct dialing format is simply followed by the 10-digit number.
Dialing and Scams
How to Correctly Call Mexico (Current Method)
To call a Mexican mobile phone from the US or Canada today, the dialing procedure is:
011 (Exit Code)+52 (Country Code)+10-Digit Mobile Number
Scam Potential
The 521 area code is not typically associated with phone scams. However, any call that appears to originate from a Non-Geographic Area Code (NGPA) or from a country code you do not recognize should be treated with caution.
- Non-Geographic Code (521): If a voice call comes from (521) XXX-XXXX, the number is likely spoofed or originates from an automated telemarketing system.
- Mexican Code (+52): While not inherently a scam code, high international rates apply, and if you receive an unexpected call, it is always safest to let it go to voicemail.
Frequently Asked Questions (FAQ)
Is 521 a geographic area code in the US?
No. 521 is a Non-Geographic Area Code reserved for specialized telecom services in the US and Canada. It does not correspond to a specific city or state.
How do I dial a Mexican mobile phone number now?
You must use the country code followed by the full 10-digit number. You should omit the extra “1” that was previously required when dialing internationally to a Mexican cell phone.
What is the time zone for the 521 area code?
The 521 area code does not have a time zone because it is Non-Geographic. It is only used for network routing and special services. If you are communicating with a contact in Mexico (Country Code +52), you must check the time zone of their specific location (e.g., Mexico City is in the Central Time Zone).
