Area Code 1357 – Iwanai, Hokkaido

Overview of Area Code 1357

Area code 1357 is a geographic numbering plan area (NPA) within the Japanese telephone numbering plan, specifically assigned to the town of Iwanai and its surrounding communities in the western part of Hokkaido, Japan. This code is part of the national destination code (NDC) structure defined by the Ministry of Internal Affairs and Communications (MIC) and administered under the ITU-T E.164 international standard. The region is served by the fixed-line PSTN (Public Switched Telephone Network) and is also accessible via VoIP services that support geographic numbering.

Geographic Coverage and Administration

The 1357 area code covers the Iwanai District, including the town of Iwanai and adjacent areas such as the village of Kyowa. These communities are located along the Sea of Japan coast, south of the Shakotan Peninsula. The code is administered by NTT East, the regional incumbent carrier, though other carriers (e.g., KDDI, SoftBank) may also provide fixed-line services in the area. As a geographic code, it is tied to a specific physical location, and calls are routed based on the subscriber's registered address.

Dialing Formats and Caller Instructions

For local callers within Japan, the number is dialed as 01357-X-XXXX, where the leading '0' is the trunk prefix. The total subscriber number length is 7 digits after the trunk prefix, making the complete national significant number (NSN) 10 digits (including the area code). For international callers, the format is +81 1357-X-XXXX, omitting the leading '0'. For example, a local number might be 01357-2-3456, which would be dialed internationally as +81 1357-2-3456.

When calling from abroad, you must replace the '0' with Japan's country code (+81) and drop the trunk prefix. If you are using a mobile phone or VoIP service that requires an international prefix, dial your country's exit code (e.g., 011 from the US, 00 from most European countries) followed by 81 and the area code without the leading zero.

Overlay and Numbering Considerations

As of the latest MIC updates, there is no overlay code for the 1357 area, meaning the area code is unique to this region. However, with the migration toward IP-based telephony, some subscribers may have geographic numbers that are not physically located in the area, but the number remains associated with the Iwanai exchange for routing purposes. For emergency services, callers should dial 110 (police) or 119 (fire/ambulance) regardless of the area code.

For businesses, having a 1357 number reinforces a local presence in Iwanai, which can be beneficial for customer trust and local SEO. However, with the rise of cloud-based phone systems, it is possible to obtain a 1357 number and forward calls to any destination, making it a flexible option for remote operations targeting this region.