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E.164 is an ITU-T recommendation, titled The international public telecommunication numbering plan, that defines a numbering plan for the worldwide public switched telephone network (PSTN) and some other data networks.

E.164 defines a general format for international telephone numbers. Plan-conforming numbers are limited to a maximum of 15 digits, excluding the international call prefix.[1] The presentation of a number is usually prefixed with the plus sign (+), indicating that the number includes the country calling code. When dialing, the number must typically be prefixed with the appropriate international call prefix (in place of the plus sign), which is a trunk code to reach an international circuit from within the country of call origination.

The title of the original version and first revision of the E.164 standard was Numbering Plan for the ISDN Era.

Numbering formats[edit]

The E.164 recommendation provides the telephone number structure and functionality for three categories of telephone numbers used in international public telecommunication:

For each of the categories, it details the components of the numbering structure and the digit analysis required for successful routing of calls. Annex A provides additional information on the structure and function of E.164 numbers. Annex B provides information on network identification, service parameters, calling/connected line identity, dialing procedures, and addressing for Geographic-based ISDN calls. Specific E.164-based applications which differ in usage are defined in separate recommendations.

The number categories are all based on a fifteen-digit numbering space. Before 1997, only twelve digits were allowed. The definition does not include any international call prefixes, necessary for a call to reach international circuits from inside the country of call origination.

Geographic areas[edit]

Country Code +91 National Destination Code (optional) Subscriber Number
National (significant)
International public telecommunication number for geographic areas (maximum 15 digits)

Global services[edit]

Country Code 91
cc = 3 digits
International public telecommunication number for global services (maximum 15 digits)

[3] Figure 2


Country Code Identification Code Subscriber Number
cc = 1 to 3 digits x = 1 to 4 digits maximum = 15 − (cc + x) = 8 to 11 digits
International public telecommunication number for networks (maximum 15 digits)

Groups of countries[edit]

Country Code Group Identification Code Subscriber Number
cc = 1 to 3 digits gic = 1 digit maximum = 15 − (cc + gic) = 11 digits







This recommendation contains the criteria and procedures for an applicant to be temporarily assigned a three-digit identification code within the shared E.164 country code +991 for the purpose of conducting an international non-commercial trial. 6724837991538884"



DNS mapping of E.164 numbers[edit]




As this is effectively a free call, there is little incentive for carriers to promote e164 DNS service. The e164.arpa domain is in production status as of 2013 only in a few European nations (Austria, Czech Republic, Finland, Germany, Ireland, Lithuania, Poland, Romania, Netherlands, United Kingdom).[5] Australia conducted a trial in 2007, but then abandoned further support of .1.6.e164.arpa.[6] Many nations have no .e164.arpa implementation active.[7]

See also[edit]


  2. ^ Unnao
  3. ^ https://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-E.164-201011-I!!PDF-E&type=items
  4. ^ Geoff Huston. "ENUM Mapping the E.164 Number Space into the DNS". The Internet Protocol Journal. Cisco Systems. Retrieved 26 October 2013. 
  5. ^ "RIPE ENUM Working Group: Progress Matrix". Enumdata.org. Retrieved 26 October 2013. 
  6. ^ "ENUM trial". enum.com.au. Retrieved 26 October 2013. 
  7. ^ Russell Bryant; Leif Madsen; Jim Van Meggelen (2013-05-10). Asterisk: The Definitive Guide. ISBN 9781449332464. Retrieved 26 October 2013. 

External links[edit]