Business Week says he's worth $3 billion. Fortune pegs his worth at $1.3 billion, and Forbes brings that figure in at $1 billion.

And Donald Trump himself? Well, according to documents obtained by the New York Daily News, he puts his worth at $3.74 billion.Normally, such frivolous matters would be best left to the giants of business journalism who have nothing better to do than count fortunes of the rich and famous.

But something interesting is happening here other than quibbling over a couple of billion dollars. The grand acquisitor is suddenly selling things, making just about everybody wonder whether Mr. Midas actually might be having some cash flow problems.

In the last week, Trump said that he is negotiating to sell what was to be the crown jewel of his real estate empire - the 76-acre tract of vacant Manhattan land where he once had hoped to build Trump City. He also said he was close to finishing off a deal with Australian beer baron Alan Bond to sell the St. Moritz Hotel for $180 million.

Not only that, Trump recently took out a $12 million second mortgage on his Palm Beach, Fla., estate, Mar-a-Lago, a property for which he paid $10 million in 1986. Is that, perhaps, another sign that he could use some cash?

"No," said the Boy Wonder. "I am having quite a year."

In the last six months, Trump has bought $1 billion worth of new toys. First, he plucked the unfinished Taj Mahal casino for about $273 million, then he snagged the Plaza Hotel for $400 million, and just two weeks ago, he announced a deal to buy the Eastern Airlines Shuttle for $365 million. That's almost $1.04 billion.

Even for Trump, whose two Atlantic City casinos alone net him about $130 million a year, that's not small change.

With a $400 million mortgage and only $12 million a year in profits, the Plaza alone will cost Trump $28 million a year until he improves the bottom line.

It's hard to think of Trump as strapped for cash. But with all this buying and selling, we thought it might be a good idea to take a crack at the Trump fortune to make absolutely sure his billionaire status is safe.

Just how rich is Donald Trump?

The shocking conclusion? Very.

Ah, but is he as rich as he says he is? Not very likely, according to a slew of casino, real estate, retail and other experts who examined Trump's holdings, often on the condition that they not be identified.

But first, a word from Trump himself, the man who gets flack for putting his name on everything he owns, then turns around and makes millions doing it.

"I will tell you the secret," he said recently, leaning back in his swivel chair in the 26th floor office at Trump Tower.

Pointing to an 18-inch model helicopter sitting on his desk, he said: "I recently took over a helicopter company called RAI, Resorts Air International for my Atlantic City operations. As soon as I bought them, I repainted them; I made them immaculate.

"Now," he said, "we call it Trump Air. So far, the capacity has doubled. It's all in the management."

There is no arguing that Trump is more than a great promoter; once he buys something, he clearly manages to add the "something extra" that makes it increase in value.

Whether it increases as much as Trump claims is another matter.

Take the case of the St. Moritz hotel:

Last week, Trump made headlines when he reported that he would sell the Central Park South hostelry for $180 million to Alan Bond.

Bursting with pride, Trump told journalists that he had paid just $31 million to Harry Helmsley for the 775-room hotel in 1985. The problem is, say Helmsley sources, Trump actually bought the place for $72 million. And real estate documents reveal Trump has an $80 million mortgage on the property. "I took a mortgage out for $50 million more than I paid," Trump says flatly.

So did Trump make a great deal on the property? The answer is an unequivocal yes. But it's unlikely he did as well as he said he did.

Trump's worth is best broken down between casinos, real estate and everything else. Not surprisingly, it is his two casinos - Trump Plaza and Trump's Castle - that have fueled the Trump empire.

Using figures based on recent casino sales in Atlantic City and Las Vegas, Drexel Burnham Lambert analyst Daniel Lee said Trump's casinos are worth $1.1 billion. If you subtract about $572 million Trump still owes on the properties, you get a figure of $528 million in equity from casinos, which is about what Trump privately claims they are worth.

"That's at least half his personal wealth," says Lee.

But using the standard method of multiplying the properties' cash flow 61/2 times, Janney Montgomery Scott analyst Marvin Roffman came up with a smaller figure of $228 million for both properties.

Trump's real estate holdings are even trickier, since no one knows what undeveloped real estate is worth until it's actually sold.

Trump privately has claimed his Trump City tract is worth $750 million. William Zeckendorf, reportedly by far the most serious negotiator talking to Trump, actually is negotiating a price closer to $500 million, according to sources. And much of that price is contingent on Trump or someone else getting the much-needed zoning improvements from the city.

His other properties - Trump Tower, Trump Castle, Trump Parc, 100 Central Park South, the New York Foundling Hospital site and a 20 percent interest in Starrett City in Brooklyn add another $420 million to his net worth, he says.

But retail expert Michael Hirschfeld, of the company bearing his name, says the retail component of the Trump Tower is probably worth $100 million. Add to that the 160,000 square feet of office space that could go for as much as $400 a foot, and you have a total of $164 million. A bundle, to be sure, but less than the $250 million that Trump claims.

Our bottom-line guess is that Trump is worth less than his $3.7 billion figure, but much more than $1 billion.

If you peg his casinos at $300 million, Trump Tower at $164 million, Trump City as $300 million (remember, he hasn't sold it yet), the Grand Hyatt at $150 million, other real estate holdings at $300 million, and the St. Moritz at $100 million, the total comes to about $1.3 billion. Add to that about $400 million in cash and securities, and the figure balloons to $1.7 billion.

Why would a man who has accomplished so much in so little time feel the need to stretch the truth when it comes to his fabulously grand empire?

A word from the master marketer himself here might be is instructive:

"A little hyperbole never hurts," he said once. `It's an innocent form of exaggeration - and a very effective form of promotion."