Area Code 91 – Mobile Network
The phone area code for Mobile Network is 91 (international format +8491). Browse local exchange codes (NXX) and carrier assignments below.
Overview of Vietnam's +84 91 Mobile Prefix
The +84 91 prefix is a non-geographic mobile network code assigned within Vietnam's national numbering plan under ITU-T E.164. Unlike geographic area codes, which correspond to specific provinces or cities, the 91 prefix is used exclusively for mobile services, making it location-independent. Subscribers can be reached anywhere in Vietnam, and the number does not indicate the caller's or callee's physical location. The prefix is managed by the Vietnam Telecommunications Authority (VNTA) under the Ministry of Information and Communications.
Technical Format and Dialing
Vietnamese mobile numbers using the 91 prefix have a total length of 10 digits when dialed domestically, including the leading '0'. The international format omits the trunk prefix '0' and uses the country code +84, followed by the 9-digit subscriber number. For example, a typical number is 091 234 5678 domestically, which becomes +84 91 234 5678 internationally. When dialing from abroad, users must replace the leading '0' with +84. From within Vietnam, callers can dial the full 10-digit number (including the '0') for both local and long-distance calls, as there are no separate trunk prefixes for mobile numbers.
Carrier and Porting Information
The 91 prefix is historically associated with MobiFone, one of Vietnam's three major mobile network operators (MNOs). However, due to mobile number portability (MNP) regulations introduced in Vietnam, subscribers may retain their 91 numbers when switching to other carriers. Therefore, the prefix alone does not guarantee the current network operator. For SMS and voice routing, the prefix is used to identify the home network for interconnection purposes, but after porting, routing is handled via a centralized database.
Usage and International Considerations
Numbers with the 91 prefix are widely used for personal and business communications. They support standard GSM/UMTS/LTE services, including voice, SMS, and mobile data. For international callers, it is essential to use the correct international dialing format: +84 91 xxx xxxx. When sending SMS from abroad, the same international format is required. Charges for international calls to Vietnamese mobile numbers vary by carrier and are typically billed at international rates. There are no special restrictions on calling these numbers from overseas, but some VoIP services may require the full international format to connect properly.
In summary, the +84 91 prefix is a vital part of Vietnam's mobile numbering resources, offering reliable connectivity for millions of users. Understanding its format and dialing rules ensures seamless communication both domestically and internationally.