They're trick questions, of course. In both cases, you call people based on their identity as registered by Apple and Google, respectively. In the case of Apple, the identity is associated with your Apple ID, and with Google, your Google+ account (which itself is associated with your universal Google ID and password). The same goes for Skype: A basic account involves the setting up of an ordinary username.
VoIP and Internet-based phone systems don't need "phone numbers," obviously. And neither did regular telephones, originally.
Where Phone Numbers Come From
The very first phone accounts didn’t have numbers at all. Telephone operators had to know everybody. But then, around 1880, they decided that this was risky because if the operators got sick in a pandemic the phone system wouldn't work. So they assigned each phone a number.
A century ago, telephones still didn't have any way to dial a number -- no rotary dial, no buttons. Picking up the receiver of a pre-dialer "candlestick telephone," used by millions of Americans between 1890 and 1920, connected you with a human operator at a switchboard. You would then ask the operator to connect you with another person in town: "Good morning, Mabel. Hey, connect me with George down at the general store, will you?" etc. If they didn't know the person, you had to tell the operator the number.
Because Mabel didn't scale, rotary dials were introduced so that people could connect calls themselves. The user of telephones was intimately connected to the phone system’s functionality, using the same number the telephone company used for "addressing" and also involved in geography of it -- long distance numbers required an "area code" and countries needed a "country code." You had to send a command beforehand to alert the system of a long-distance number by dialing a "1."
Phone numbers made sense, because the idea of building a phone with an alphanumeric keypad was impractical. Besides, the concept of associating a phone number with a person, rather than a building, hadn’t been thought of yet.
Mabel Is Back!
Ironically, the idea of picking up the phone and telling someone who we want to call is how phones work nowadays. When I use an iPhone, I press and hold the Home button, then tell Siri: "Call George." When I use my Moto X or Google Glass, say either "OK, Google Now: Call George" or "OK, Glass: Make a call to George."
It's exactly like 100 years ago, except the operator is a virtual human. Unlike Mabel, Siri can remember all the numbers. And she never gets sick.
Yes, at some point I have to know somebody's phone number and enter it into my contact app, if I want to reach a conventional number. But my knowledge and use of the number is simply a needless throwback at this point -- it's like using an IP addresses to email somebody's PC, rather than using their email username.
The absurdity and obsolescence of telephone numbers is made spectacularly obvious by anyone who uses Google Voice, as I do.
When you sign up for Google Voice, they give you a unique phone number, but only because everybody expects to use phone numbers. People are stuck in the past, and Google panders to that flaw of human nature. They let you pick any area code you want -- I picked the New York area code 646 even though I don't live anywhere near New York, making a mockery of the whole "area code" concept.
You can tell Google Voice to ring a landline phone, a cell phone, or your laptop -- or all three at once. When people call your phony Google Voice phone number, it rings any phone you want. And you can set it up to change this automatically based on the time of day, or change the phones it rings every day for any reason. When you put callers on the blocked list, Google Voice will lie to them with a fake "this number is no longer in service" recording.
In short, Google Voice lets you do anything you can think of with an Internet-connect phone, while at the same time coddling obsolete expectations with the various trappings of old-fashioned telephone service.
In reality, my "phone number" is just my Google ID. When people call me, they call, well, me. Not a building. Not a number. And I can tell any phone to ring depending on where I am.
It appears that Google may, in fact, be heading toward phasing out phone numbers. The new version of Android, code-named KitKat, is now search based. The default mode is to simply type the person or business's name, and the dialer app will search both your contacts and Google Maps.
We also learned this week that within six months or so, Google's Android OS will automatically connect to your contacts' Google+ accounts, sucking in their profile picture (and all other user contact information) into your phone's phone dialer.
This is no big deal to users -- there have long been apps and services that bring social media profile pictures into contact apps as a convenience.