As soon as an actor in a movie or TV show starts rattling off a phone number, every viewer knows what the first three digits will be: 5-5-5. How did “555” become the convention for fake phone numbers, and are there any real 555 numbers? Let’s dial up some answers.

Why do TV and movies need the fake 555 numbers? Just ask anyone who had the misfortune of having the number 867-5309 how their life changed after Tommy Tutone's 15 minutes of fame. Apparently some tiny fraction of the population—we’re guessing a fraction that largely consists of adolescent boys—thinks it’s hilarious to call any number they see on the screen. To curb these nuisance calls, movies and shows have been using the fake 555 numbers since as far back as the 1950s. (In keeping with the old exchange-naming convention, back then it was “KLondike 5” or “KLamath 5.”)

It’s hard to pin down exactly how 555 became the go-to fake prefix for phone numbers. In the book Easy as Pi: The Countless Ways We Use Numbers Every Day, author Jamie Buchan speculates that the repeated digit may have made the combination memorable, which helped it gain traction. Buchan adds that since no major place names in the United States began with a combination of the letters J, K, and L (the letters assigned to the 5 key on a phone), the KLondike/KLamath prefix wasn’t exactly a coveted commodity.

Since the early 1970s there’s been at least one 555 number callers can dial and get an answer—555-1212 is a standard number that rings directory assistance. The rest of the 555 numbers have largely gained fame as fake numbers in movies and on TV. (The number 555-2368 has risen to particularly rarefied air, possibly because of the “2368” combo’s use in old phone ads. Dialing 555-2368 will get you the Ghostbusters, the hotel room from Memento, Jim Rockford of The Rockford Files, and Jaime Sommers from The Bionic Woman, among others.)

Real Fake Numbers

What you may not know, though, is that there are many more “real” 555 phone numbers. Since 1994, 555 numbers have actually been available for personal or business use. That’s when the North American Numbering Plan Administration started taking applications from people and businesses who wanted their own 555 numbers. Theoretically, these numbers would have worked from anywhere in the continent; dialers would be able to dial 555-XXXX and always end up with the same number regardless of area code. The hope was that if you needed, say, a taxi anywhere in the country, you could just remember one number that would always work.

Things didn’t work out quite so smoothly. People and businesses snapped up the 555 numbers —except for 555-0100 through 555-0199, which were held back for fictional use—but they soon learned that owning a phone number isn’t all that useful if you don’t also own a phone company that can connect the number. Phone companies protested that setting up these services would be wildly expensive; in 2003 Verizon told The New York Times that adding the nationwide 555 service to its systems would cost the company $108 million. (Verizon did offer to hook up the 555 numbers for owners, but the same Times story noted that the service usually required a $2,500 set-up fee per area code.)

Skeptics claimed that the phone companies were just dragging their feet so the 555 numbers didn’t sap cash away from 800 numbers. There may be some truth to that theory, but the 555 system still isn’t up and running in any meaningful way. The list of people and entities that own the numbers is a pretty amusing read, though. It’s mostly newspapers, hospitals, random people, and the state of Nevada.