E.164 is an ITU-T recommendation, titled The international public telecommunication numbering plan, that defines a numbering plan for the world-wide Public Switched Telephone Network (PSTN) and some other data networks.

E.164 defines a general format for international telephone numbers. Plan-conforming Phone Numbers are limited to a maximum of 15 digits, excluding the international call prefix.

The presentation of a Phone Number is usually prefixed with the plus sign (+), indicating that the Phone Number includes the Number Plan Area. When dialing, the Phone 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".

More Information#

There might be more information for this subject on one of the following:
  • [#1] - E.164 - based on data observed:2015-05-18