It's catching on. One hundred hours, that is. Or rather, "100 Hours." That's how long the ground war against Iraq took, and that's the way it's starting to stick in people's minds and jump off people's tongues: "100 Hours."

That's more than just luck. Not that anybody expected the ground campaign to last precisely that long. But when it all went so well so quickly, the time came to think about calling it quits.And that's when, according to the stories, someone in the White House with "a sense of history" (and good number skills) noticed, more or less: "Hey - if we shut this thing down at midnight tonight, it'll be exactly 100 hours since we started!"

"A sense of history" - and a sense of marketing. The president used "100 Hours" when he went on TV; he used it again when he spoke to Congress. The president's people have been using it, too, every chance they get. But it's not only the president's people; newscasters, commentators - all those molder-and-shaper types - have been using it themselves.

You've got to hand it to the White House: It's brilliant. A good round number - easy to remember, easy to say.

Not that it absolutely had to be a round number, mind you, although "100 Hours" does fill the gap between "101 Dalmatians" and "99 Bottles of Beer on the Wall," which is probably a good thing.

I like the "Hours" part of it, too; it not only smacks of speed, it avoids a potentially messy diplomatic incident. "100 Hours" translates to "Four Days," or "Four Days with a Little Bit Left Over," if you want to get technical about it. The problem is our good friends the Israelis.

They're already sitting in the Guinness Book with their famous "Six-Day War" back in 1967; calling our stroll through the desert a "Four-Day War" (especially since it wasn't the whole war, the way theirs was) might look as if we were trying to show them up - not a good idea, considering all the Scuds they were willing to swallow for the cause this time around.

Sure, "100 Hours" is still shorter than "Six Days," but most people won't bother doing the math, so the Israelis will probably be cool about it.

When it comes to other wars, though -even whole wars - it's no contest. The Thirty Years' War, for instance, not to mention the Hundred Years' War (which actually ran more like 116 years, which just goes to show how sloppy people can get about record-keeping when they let these things drag on).

"54-40 or Fight!" "Thirty Seconds Over Tokyo!" "30 Days to a Flatter Stomach!" That's what American history's all about: Playing by the numbers. Just call the roll and see for yourself: "A Thousand Clowns." "Seventy-six Trombones." "Three Men and a Baby." "2 Live Crew."

You've got to admit, "100 Hours" is right up there with the best of them. It's a number with the taste of destiny. Back at the White House, they couldn't be happier. They've already got their eye on another number. 1992.