From http://en.wikipedia.org/wiki/E.164
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 numbers are limited to a maximum of 15 digits. The presentation of numbers is usually prefixed with the character + (plus sign), indicating that the number includes the international country calling code (country code), and must typically be prefixed when dialing with the appropriate international call prefix, 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".
Google phone parser:
Github:
https://github.com/googlei18n/libphonenumber
Demo:
http://libphonenumber.googlecode.com/svn/trunk/javascript/i18n/phonenumbers/demo-compiled.html
https://www.twilio.com/lookup