Area Code 1635 – Hamatonbetsu, Hokkaido

Geographic Overview

The +81 1635 area code serves the Hamatonbetsu region, located in the northern part of Hokkaido, Japan's northernmost main island. This area code is part of the Hokkaido telephone numbering plan, specifically covering the town of Hamatonbetsu and its surrounding areas within Esashi District (Hiyama Subprefecture). The region is known for its coastal location along the Sea of Japan and its proximity to natural landmarks such as Cape Sōya, the northernmost point of Japan. Major nearby cities include Wakkanai, which is approximately 50 kilometers to the north, and Nayoro to the southeast.

Dialing Formats

When calling a landline in Hamatonbetsu from within Japan, you must dial the area code (including the leading zero) followed by the subscriber number. The area code is 01635 when dialed domestically. For example, a local number such as 2-3456 would be dialed as 01635-2-3456 from elsewhere in Japan. When calling from abroad, you must omit the leading zero and use the country code for Japan (+81). Thus, the same number would be dialed as +81 1635-2-3456 from an international line.

Geographic Coverage and Jurisdiction

The 1635 area code is allocated to the town of Hamatonbetsu, which is administered under the Hokkaido Prefectural Government. The coverage area includes the central urban district of Hamatonbetsu and its rural outskirts. The numbering plan follows the ITU-T E.164 recommendation, with the country code +81, a National Destination Code (NDC) of 1635, and a subscriber number that typically consists of 4 to 6 digits, resulting in a total number length of 10 digits (including the leading zero) when dialed domestically.

Caller Instructions

For callers within Japan, simply dial the area code with the leading zero (01635) followed by the local number. For callers from outside Japan, replace the leading zero with +81 and then dial 1635 followed by the subscriber number. There are no overlay codes in this region, so the 1635 area code is unique to Hamatonbetsu and does not require additional digit dialing. Calls to Hamatonbetsu from mobile phones or VoIP services may incur additional charges depending on the caller's plan, but the dialing format remains the same.

Technical Considerations

This area code is a geographic code, meaning it is tied to a physical location and is used for fixed-line services. It is not portable to other geographic regions, and number portability within the same area code is possible but limited to the same service provider. The region is served by NTT East, the dominant fixed-line operator in Hokkaido, but alternative carriers may also offer services using this code. For international callers, it is important to note that Japanese area codes are not used for mobile numbers; mobile numbers in Japan begin with 070, 080, or 090. Therefore, +81 1635 numbers are exclusively landlines.