A NANP (North American Numbering Plan) divides +1 numbers into three groups. In the days before number portability where numbers were fixed to a geographical area, the number couldn’t go with you, and you would be stuck with what was available. The 1st-3rd numbers are the area code. 4th-6th numbers are the exchange, and the last four numbers are the subscriber number. Combining all three groups will be the telephone number. Some large entities with a need for thousands of telephone numbers could acquire their own exchange. I will imagine that this will still hold true.
The 555 exchange is reserved for fictional numbers. With that said, I am confident that I would not be giving away people’s numbers by using the 555 exchange in my sites. Even so, I would almost never include the area code which makes it much harder for a SPAM bot to find an actual phone number. While I will likely never acquire my realty company, I will want either 412-377 or 878-377 numbers. This is 10,000 numbers, and assuming that an exchange is $20,000 – this is about $2 per number, but I will be required to still have phone service. I will imagine that I would have a control panel to allow me to distribute my numbers as I see fit. If the bill is not paid for whatever the reason, the number will be returned to me, but will provide for a “Number Not in Service” error message when calling a non-active number. If I was to acquire the above mentioned exchanges, then the main number will take the 7368 subscriber number. This number spells out RENT on the number keypad making it easier to remember the number. I may also do something similar for the PMB, Convenience Store, and Pharmacy. Since the entire exchange will be mine, it would just make more sense to have numbers like MAIL, FOOD, or DRUG for the various businesses.