Area Code 1644 – Rumoi, Hokkaido

Overview of Area Code 1644

Area code 1644 is a geographic National Destination Code (NDC) assigned to the city of Rumoi and its surrounding municipalities in the northern part of Hokkaido, Japan. This code is part of the Japanese telephone numbering plan, which follows the ITU-T E.164 standard. When dialing from abroad, the full international format is +81 1644, followed by the local subscriber number. Within Japan, callers must dial 01644 before the subscriber number, as the leading zero is part of the domestic trunk prefix.

Geographic Coverage and Jurisdiction

The 1644 area code serves the Rumoi Subprefecture, including the city of Rumoi and the towns of Obira and Tomamae. This region is located on the northwestern coast of Hokkaido, facing the Sea of Japan. Rumoi is known for its fishing industry and scenic landscapes, while Obira and Tomamae are smaller rural communities. The administrative jurisdiction falls under the Hokkaido Prefectural Government, and the area is served by NTT East (Nippon Telegraph and Telephone East) as the primary local exchange carrier.

Dialing Formats and Caller Instructions

For local callers within the 1644 area, it is possible to dial the subscriber number without the area code in some cases, but the standard practice is to dial the full 10-digit number (including the leading zero) to ensure connectivity. For example, a local call to a subscriber number 123456 would be dialed as 01644-123456 from anywhere in Japan. For international callers, the number must be dialed as +81 1644 123456, omitting the leading zero of the area code. When calling from a mobile phone in Japan, it is also necessary to include the area code, as mobile numbers are not geographically tied and require the full national number.

Overlay and Numbering Considerations

Currently, there is no overlay code for the 1644 area, meaning that the area code is unique to this region. However, as with all Japanese geographic codes, the subscriber numbers are typically 6 to 7 digits long, making the total national number 10 digits when including the area code. The Japanese government has been considering number portability and VoIP integration, but for traditional PSTN lines, the geographic significance remains. Callers should be aware that some VoIP services may allow the use of the area code without the leading zero, but for standard PSTN and mobile calls, the format 01644 is required domestically.

Practical Examples

To illustrate, if you are calling a business in Rumoi from Tokyo, you would dial 01644-XXXXXX. From the United States, you would dial 011 81 1644 XXXXXX. From a European country, the international prefix (00) would be used: 00 81 1644 XXXXXX. Always ensure you have the correct subscriber number, as the area code alone does not complete the call.