The iNum Initiative is an effort by Voxbone to create an international “country code” for VoIP communication. An iNum number (or simply an iNum) starts with the country code +883 (allocated by the ITU followed by the “area code” 5100, followed by eight unique digits. For example, my own iNum is +883 5100 0990 4862.

iNums serve two purposes/accomplish two goals:

  1. They facilitate free calling between VoIP providers.
  2. They help ensure that calls between VoIP providers don’t get routed through the PSTN.

Let’s look at the first goal. Any user of a VoIP provider that offers iNums as DIDs can make free calls directly to iNums. Some VoIP providers that don’t offer iNums also complete direct iNum calls for free. The system is funded by people directly calling iNums from the PSTN, in which case the PSTN provider can choose the price they wish to charge per call. PSTN-to-direct-iNum call prices range from $0.032/minute to $9.99/minute, depending on the provider and how they classify the destination number.

Now, let’s take a look at the second goal. Ideally, calls between VoIP providers would always route completely through the Internet and avoid routing through the PSTN. Why? Because routing through the PSTN degrades call quality and increases connection times. iNum is designed so that calls betweem VoIP providers that offer iNums route completely through the Internet.

There are a few different ways to call a person with an iNum:

  1. Directly dial the iNum.
  2. Dial the iNum through a local access number.
  3. Dial the iNum as a SIP address.

The first method is the best one. Ideally, all providers will eventually offer direct dialing to iNums. Right now, the providers that offer direct dialing to iNums include all VoIP providers that offer iNums, a few VoIP providers that don’t offer iNums, and a few PSTN providers. Viber offers direct dialing to iNums for free, even without any ViberOut credit. Google Voice and Skype used to offer free direct dialing to iNums, but have started charging for it.

The second method allows traditional PSTN users and non-iNum VoIP providers to dial iNums. The user simply dials a local access number, waits for the prompt, and then dials the iNum. This method may also end up being cheaper than direct dialing iNums if your provider charges too much money for direct dial.

The third method allows SIP users to dial iNums. The iNum is suffixed by, turning it into a SIP address. For example, my iNum as a SIP address would be

If you have an iNum, feel free to contact me and let me know which method you used, who your provider is, etc.