Ok, 7 digits. Can’t start with 0 or 1. That cuts it to 8 million. Can’t start with 555, 911, 411, etc. Rough guesstimate is that it’s over 7 million. Can we get more precise?
Number of prefixes, 000-999: 1000
Remove 555, 0xx, and 1xx: 799 prefixes left
Remove x11: 791 prefixes left
At 10,000 numbers per prefix, that would be 7.91 million numbers per area code.
And for the “old-timers” who may recall otherwise from the days of mechanical switching systems - 0 and 1 used to be reserved digits that could not be the middle digit of a prefix. Original usage was area codes had 0 or 1 as the middle digit, but that’s no longer the case as the current computerized switches don’t care.
Just because there are 7.91 million phone numbers per area code doesn’t mean that there are 7.91 million numbers per area code. Granted this story is about 5 years old and things may have changed since then, but I don’t think so.
FTR, it is NANPA that doles out the area codes in North America.
Despite the fact that there are still plenty of phone numbers available in most area codes, it looks like the FCC is toying with the idea of adding an additional number to area codes and exchanges based on a recommendation:
The rate of telephone-number takeup has slowed dramatically in the NANP in the last few years. As methods of assigning telephone numbers become more efficient (you no longer have to give an entire exchange of 10000 numbers to a phone company with only a dozen customers in the area, for instance), many plans to add area codes have been delayed or even cancelled.
We won’t be needing twelve-digit numbers anytime with the next couple of decades. Which is good, because it will take that long to revamp the entire phone-switching system to accomodate them.
No, actually, 555- is a valid prefix. Looking through our Fayetteville, Arkansas phone book, (Ok, I’m not actually doing that, I’m in Germany) you can see many 555- numbers.