IT HAS A POWERFUL RING

LIKE body fat percentages and box office grosses, area codes are one more metric by which Southern Californians define themselves.

The broad stereotypes (and are there any other kinds when you’re lumping millions of people together?) include the old-school, loft-dwelling 213; the knit-cap-wearing, hipster-vegan 323; the moneyed, three-picture-deal 310; and the oft-maligned, suburban punch line of the 818.

Which brings us to the 424.

If the mention of those digits makes your eyes glaze as you mentally thumb the Rolodex of the mind, you’re not alone.

In an informal survey of co-workers, passersby and the occasional grocery-store bagger, most had never heard of — much less dialed — the 424 area code.

But the 424 does exist — with nearly 35,000 numbers assigned since it rolled out in August. And how it exists threatens to end the numerical Balkanization of the Southland — at least in geographic terms.

Numerically, the 424 falls just between parts of Tennessee (423) and the Seattle suburbs (425), but telephonically the freshly minted digits cover the same area served by the 310 (West Los Angeles, Beverly Hills and the South Bay). That’s because instead of splitting an existing area code (like the 310, which was cleaved from the 213 in 1991), the California Public Utilities Commission adopted the state’s first overlay, slapping the 424 only on newly assigned numbers in the same area.

The end result is a set of digits that says less about where one lives than it does about when the person moved there — a kind of “born-on” date for new residents. (And feel free to come up with your own catchy mnemonic device. Something like: “If he’s got digits with the 424 / He’s from August ’06 and not before.”) What’s next? Handing out signs at LAX that say “Fresh off the turnip truck”?

But there is one segment of the population that has the 424 taped to their cubicles, programmed into their phones, burned into their brain stems and hard wired into their souls, and they’re the ones with the power to shape the 424 of the future: the 700-odd employees of the Creative Artists Agency, their clients and the legions who frantically dial the phones on their behalf.

CAA, known for routing all its calls through a single number (which until recently was [310] 288-4545 — a number that one entertainment industry assistant called “the best-known number in Hollywood”), found itself branded with the 424 when it relocated to new Century City digs in January. But following so quickly on the heels of the new overlay, the new area code instantly became associated with the agency, more a badge of honor than a scarlet letter.

“The 424 is pretty much CAA,” said a cable-channel assistant (who, like the rest of the faceless infrastructure that runs Hollywood, can’t get permission to speak on the record, even about area codes). “No one heard of it before they moved there, and it hasn’t popped up anywhere else since.”

A CAA assistant cited a similar experience. “It’s just us, that’s all I know about [the 424].”

The perception of the 424 as CAA’s private area code has even crept beyond the entertainment industry, reinforced by the fact that other new nearby tenants (including talent agency ICM and several businesses in the same building as CAA) have managed to keep the 310. Alyson Domoto, an attorney who works in Century City, is one of those perplexed. “Yeah, what is up with that?” she responded when queried about the code. “Does CAA get its own code or what?”

Although that impression may fade as new numbers continue to populate the Westside, for now the fledgling 424 is the perfect reflection of the Los Angeles dichotomy: The person on the other end of the line could just as easily be the newest kid on the block or the next kingmaker. You won’t know until you pick up the phone.