Area Code 631 – Sibolga/Pandan

Geographic Coverage and Administrative Jurisdiction

Country code +62 is assigned to Indonesia under the ITU-T E.164 international numbering plan. The national destination code (NDC) 631 is a geographic area code serving the western coastal region of North Sumatra (Sumatera Utara) province. Specifically, the 631 area code covers the city of Sibolga and the adjacent municipality of Pandan, which is the capital of Central Tapanuli Regency (Tapanuli Tengah). This numbering area is situated on the western shore of Sumatra, facing the Indian Ocean, and is distinct from the larger Medan metropolitan area (code 61) to the north.

Dialing Formats and Caller Instructions

For domestic callers within Indonesia, calls to any fixed-line subscriber in the Sibolga/Pandan area must be dialed using the trunk prefix 0 followed by the area code and the subscriber number. The complete domestic format is 0-631-XXXXXXX, where X denotes the 7-digit local subscriber number. For example, a local number might be dialed as 0-631-1234567.

International callers must replace the leading 0 with Indonesia's country code +62, resulting in the international format +62-631-XXXXXXX. For instance, a caller from abroad would dial +62 631 1234567. It is essential to omit the trunk prefix 0 when dialing from outside Indonesia.

Numbering Plan and Overlay Considerations

Indonesia's national numbering plan (based on the Ministry of Communication and Information Technology regulations) assigns geographic area codes to specific administrative regions. The 631 code is a closed numbering plan within its region, meaning that local calls within the same area code do not require the area code; subscribers can dial just the 7-digit local number. However, calls from outside the 631 area, even from other parts of North Sumatra, must include the area code with the trunk prefix.

Currently, there is no overlay code for the Sibolga/Pandan area; 631 remains the sole geographic code for this region. All fixed-line numbers in this area are 7 digits long after the area code, consistent with the national standard for non-metropolitan areas.

Practical Guidance for Callers

• Local callers within the 631 area: dial only the 7-digit subscriber number (e.g., 1234567).
• Domestic long-distance callers from other Indonesian regions: dial 0-631-XXXXXXX.
• International callers: dial your country's exit code (e.g., 00 or +), then 62, then 631, then the 7-digit number. Example: +62 631 1234567.

When saving contacts in a mobile phone, always store the number in international format (+62 631 ...) to ensure proper routing both domestically and internationally.