The nine world zones are generally organized geographically, with exceptions for political and historical alignment.
• Zone 1 uses an integrated numbering plan; four digits (1xxx) determine the area served in 展开

This table lists in its first column the initial digits of the country code shared by each country in each row, which is arranged in columns for the last digit. When three-digit codes share a common … 展开

• "List of ITU-T Recommendation E.164 Dialling Procedures as of 15 December 2011" (PDF). ITU. Archived (PDF) from the original on 10 October 2022.
• International Telecommunication Union (15 December 2016). "Complement to Recommendation ITU-T … 展开

World zones are organized principally, but only approximately, by geographic location. Exceptions exist for political and historical alignments. 展开

• Telephones portal
• List of mobile telephone prefixes by country
• National conventions for writing telephone numbers 展开