Calling an iNum telephone number

A decade ago some Internet geeks set up a new kind of telephone number — an “iNum” telephone number.  A regular telephone number always starts with a country code.  Calls to Switzerland for example use a country code of “41”.  Calls to North America use a country code of “1”.  Just by looking at the telephone number, you can see what country it is associated with.  But not iNum numbers.

The idea of an iNum number (see Wikipedia article) is that it tries to accomplish an end run around the PSTN (public switched telephone network).  I have obtained some iNum numbers and I will be trying to figure out how best to put them into use.  Here is one of the numbers:


The point of an iNum number is that you might be anywhere in the world, and if you dial that number, it will go through.  And when it goes through, hopefully it will be a free call or will cost no more than the cost of a local telephone call.  The organizers of iNum have set it up so that any telephone company can, if it wishes, connect an iNum call in a way that costs nothing (through VOIP).

It will not surprise you when I say that if you have an iNum number, you can receive calls for free.  You can be anywhere in the world, and receive calls for free on your iNum number.

Although iNum numbers have been around for a decade now, some telephone companies have not yet gone to the trouble to configure their network to handle such a call.  So depending on which telephone company use are using to place your outgoing calls, you might dial the number and maybe the call would not go through.

I would be most grateful if you, dear reader, would place three test calls to this telephone number +883-5100-0990-5635.  (Add the appropriate international prefix such as 011, +, or 00 as needed.)  Please make a first test call from your office phone (which is probably a VOIP line).  And please make a second test call from your home landline (if you have one!) which is probably a VOIP line.  And please make a third test call from your cell phone.

Your best likelihood of success is if the telephone that you are calling from uses SIP telephone service (see blog article describing our migration to SIP service which reduced our telephone bill from $160 per month to 85¢ per month).  If you have already migrated your office to SIP, then very likely you can dial the test number and have the call go through.  (Also, if you have already migrated your office to SIP, then very likely you could get your own iNum telephone number for incoming calls so that SIP users all around the world could call you for free.)

I hope that readers from every country around the world will try this so that I can get a good sense of how many phone companies around the world have gotten this working.

When you place a test call, it might not go through.  See below for a suggestion what you might want to do if the call does not go through.  If the test call does go through, you will hear my voice and I will invite you to leave a telephone message.  Please leave a message letting me know what country you are calling from, and which telephone company you are using to place the call.  Later I will collect everybody’s messages and I will aggregate them and post a followup article describing the results.

If the call does not go through on a particular carrier, please consider sending a polite letter (here is a template) to that carrier.

The alert reader might ask “how may I get one of these trendy, modern and up-to-date iNum telephone numbers?”  And the answer is, if you are using VOIP for your telephone service, probably your VOIP provider will give you an iNum telephone number free of charge.  In our office, we use for most of our VOIP needs, and they gave us an iNum number free of charge.

Again, dear reader, thank you for making the three test calls.

6 Replies to “Calling an iNum telephone number”

  1. I use 1-VOIP for my phone service at similar prices. I also have an app called Zoiper which allows me to use my cell phone, tablet, or computer to connect over Wi-Fi and make calls using my VOIP lines. The great thing is, I could be in a café in Tokyo and make a call over Wi-Fi to a US number, and it would cost me nothing because I have unlimited calling on my VOIP lines. Also, the caller ID will show up as my US office number.

    1. Yes, the modern world of SIP and VOIP is really worth getting familiar with. I also use Zoiper on my cell phone. You could call my office and they could transfer the call to my office extension, and it will ring on my cell phone as a Zoiper call. The caller might not realize they have reached me while I am seated at the next table over from you at the café in Tokyo. And if I call that party using the Zoiper app the caller ID will show my US office number.

  2. Here is some info about iNum numbers:
    1. It is improper to put the + in front of the iNum number. It implies that an international access must be dialed before the number, which it does not. Though with some providers allow the 011, it is not needed Dialing an iNum just needs the 883 xxx xxx xxx xxx.
    2. You are only able to dial iNums from VoIP phones. In order to dial an iNum form Google, regular line, or a mobile, you must dial an access number and then you can enter the iNum number. Here is a list: The benefit of this is that calling someone with a iNum is a local call (i.e. use the local access number) but of course you are dialing 10 million digits.
    3. VoIP by nature is a location independent technology. It can have a number of configurations from terminating calls to call groups, multiple VoIP endpoints, to landlines, etc. It is not call forwarding, since VoIP provides call forking and other technologies.
    4. The signalling path is separate from the voice path, so many services can be added for call routing and management while the signaling and call reporting can happen centrally.
    5. I am happy to answer other questions or figure out how we can add some services around this and file a PCT.

    1. Thank you very must for posting.

      In general yes the caller must precede the telephone number with 011 or + or 00 or whatever the local way is to signal to the system that the call is an international call. I guess in some Asterisk systems and with some ATAs the system administrator might be able to define dialing rules in which the 011 or + could be omitted. But in general there is no choice but for the caller to signal in some way that the first few digits are a country code and not an area code or city code.

      As to who can successfully dial an iNum call, you are quite right that the telephone carriers that most consistently support iNum destinations are SIP (VOIP) carriers. But there are exceptions each way to the rule. Some SIP (VOIP) carriers fail to support calling iNum destinations. And there are some non-SIP carriers that do carry iNum calls. For example just in the past 15 hours I received reports for multiple persons that from their Verizon cell phone, they were able to dial the iNum call.

      Again thank you for posting.

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