Hacker News new | past | comments | ask | show | jobs | submit login

Given that the population of Japan is <130M and is only going to go down from now on, what's the point? :)

14-digits?!?! Yikes. Not looking forward to using that!

For those that haven't RTFA Japanese phone numbers have 11 digits, 123-1234-1234, of which the first three are reserved as identifiers. A lot of people also carry two phones. Many companies also still have fax machines. Even my pocket wifi has its own phone number (can't be dialed).

8 digits is only 100,000,000 possible unique numbers. So it looks like they're simply running out of numbers.

>Japanese phone numbers have 11 digits

10 digit numbers are still in use:


I've always thought of those as having an invisible 0 that's filled by the system, like when you call a landline number.

If the first three are reserved, why not just expand on those? There are sufficient 3 digit combinations for whatever they would need.

Good question. Who knows?

When Singapore ran out of phone numbers, they simply tacked on a single digit to every existing phone number. Japan's population is dwindling, that seems like a much easier option.

> 8 digits is only...

Sure, but the US with a much larger population only uses 10. 14 is bonkers, especially if it's just to preserve a method that basically wastes 3 of them.

"identifiers" just means "area code", they're not wasted

As a user of this numbering system, this is how it generally looks like:

Landline numbers are dialed

0 - prefix to dial outside my area code

XX(X) - area code

XXX-XXXX - phone number

Mobile phones are

0 - prefix

70/80/90 - "mobile phones" area code

XXXX-XXXX - phone number

Since every number starts with a 0, you don't think of it as part of the number. Without the 0, most landlines are 9 numbers long and mobile phones are 10 numbers. When you're calling between landlines in the same area code, you only need 7 numbers.

The largest issue is the death of landlines and the rise of mobile phones. Lots of area codes dedicated to landlines when landlines are dying.

The NANP (north american numbering plan) is basically the only place in the world where cell phones get put into regular geographic area codes, due to the way cell phones are billed there (in the rest of the world, receiving calls on a cell phone is free, the caller pays the extra fees)

Fyi, Mexico (+52) and Argentina +(+54) have mobile and landline integrated into the same geographic numbering, although there's an extra digit for dialing a mobile, to indicate cost (will be phased out in Mexico soon)

Brazil (+55) has mobile in geographic area codes, but separate prefixes within the area codes and longer than landlines (except for Nextel, which is a radio phone, not a mobile phone).

Some countries have been getting mobile phones in landline ranges as tarriff arbitrage, like Germany (+49) and Russia (+7, along with Kazakhstan, but I think it's only getting fuzzy in Russia). Others have been getting mobiles filtering in as fixed CDMA carriers using landline ranges start supporting mobile CDMA handsets (I forget where, but a few countries in Africa and southeast Asia)

Maybe there will be a checksum digit. :) Given how rarely I enter contact information in manually, it doesn’t seem that unreasonable to have a larger phone number - nowadays it’s either clicking a link, opening a QR code, or copy pasting some text to make a new contact.

I would guess that these numbers will be hard-wired to "Internet of Things" devices, and this is a move to centralize the control of them. If every device has it's own telephone number that can't be modified and a 5G modem built in then the government (via phone companies) has a huge amount of control - sending messages, commands, remotely monitoring them, bricking them...

Every device on a 3GPP network (GSM/UMTS/HSPA/LTE/5G) already has a unique IMEI burned into it (and in most countries it's illegal to reflash the IMEI since they're used to ban stolen devices), phone numbers don't matter for "government control".

Can you address a device over a cellular network by it's IMEI number? I didn't think you could. You'd need a phone number as well. Could well be different over 5G though.

The IMEI is permanently associated with the device.

The phone number (IMSI) is associated with the SIM card (or eSIM now) and can be trivially swapped out.

A network can definitely address a device by IMEI only. For example in most countries you can make emergency phone calls to 911/112 with no SIM card in your phone (and hence no phone number) and there are no troubles routing that call.

For 2G GSM the emergency calls are one big special case in the radio interface layer and do not really work as normal calls, this mechanism is triggered by dialing '112' which is hardcoded into the terminal (and does not work for other emergency service numbers, although US terminals maybe also special case 911, on European ones only 112 work).

IIRC BSC can page terminals on PCH not only by TMSI (which should be the normal state) but also by raw IMSI or IMEI, but this is not an capability that gets you anything useful as the terminal has to have active association to the network to even listen on PCH and when the device is associated the network knows the relationship between all of these three values.

The IMEI uniquely identifies the device; the IMSI uniquely identifies the subscriber.


15 is the ITU max BTW - something to be aware of for HN contributors when setting up DB Schemas that stope phone numbers.

Sorry for being cynical, but I've had my share of "things that would never happen because of standards/regulations/common sense" happen when you're storing data in DBs

Phones have at most 15 digits? I'm putting 20 or 25 just in case.

Sometimes people want to add internal extension numbers to phone numbers, so having breathing room to enter those makes sense too

I think those exist within the numbering plan, and sound extensions be a separate field in the db any how.

A system I worked on used the RDBMS’ default of 50 characters in a varchar column and the validation regex allowed uppercase alphanumeric input (for “1-800-CONTACTS”-style numbers) and also allowed spaces in addition to dashes. But the system didn’t allow users to label numbers in a separate field - so the users put the labels at the end of each number, e.g. “425-123-7890 JOHN SMITH, HOME”.

The system used this value for generating tel: links in webpages - which meant the links wouldn’t work anymore - but users preferred keeping these custom labels to having Skype-integrated or iOS tappable links anyway.


> Phones have at most 15 digits? I'm putting 20 or 25 just in case.

That's fine, but if we have to go beyond 15 digits, it will probably be an upgrade as big as going to IPv6 128-bit addresses given that the ITU has specified fifteen for a while now:

* https://en.wikipedia.org/wiki/E.164

”The communications ministry plans to create some 10 billion 14-digit phone numbers starting with “020” for assignment.”

I expect “020” isn’t currently a valid prefix in Japan. If so, this makes it a lot easier for software to know whether it has to wait for more digits in a phone number.

There probably are lots of other unused three-digit prefixes, but one has to assume what one deploys now will stay around forever (one century and counting), and that the future will demand space for things we have no idea of.

And 14 isn’t that bad. Bank accounts in Gibraltar (population 35,000 or so) have 23 characters, Kuwait’s (population 4,5 million) have 30, Malta’s (population about 500,000) 31 (https://en.m.wikipedia.org/wiki/International_Bank_Account_N...)

Except that there are already 11-digit 020 numbers in Japan, so hopefully it'll be something like 0200..0202 11-digit and 0203..0209 14-digit. Otherwise you'd need a database lookup already just for the length of the number.

> For “internet of things” devices, 11-digit numbers starting with “020” have been used since January 2017.

Machine-2-machine (M2M) communication might play a role in the big number of addresses, not sure though.

You are correct, the 020 prefix is exclusively reserved for M2M. The "conventional" 070, 080 and 090 prefixes are used for smartphones & M2M and the Japanese government has tried to move the vast majority of M2M to 020. It was already expected that the current 11 digit number for 020 is not sufficient, and AFAIK there is a plan for numbers up to 14 digits.

> Not looking forward to using that!

I thought that as well, but the more I think about it..: I'm pretty sure I did not type out a phone number for the last 5 years.

It's all numbers already saved in my contacts, new numbers I got via some form of text message or numbers on websites and the Google app.

It might be that people don't really type number all that often anymore.

Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | Legal | Apply to YC | Contact