Calculate the number 683

Before going to Europe on business, a man drove his Rolls-Royce to a downtown New York City bank and went in to ask for an immediate loan of $5,000.

The bank officer says the bank will need some kind of security for such a loan. So the businessman hands over the keys to a Rolls-Royce parked on the street in front of the bank. Everything checks out, and the bank agrees to accept the car as collateral for the loan. An employee drives the Rolls into the bank's underground garage and parks it there.

Two weeks later, the businessman returns, repays the $5,000 and the interest, which comes to $15.40. The loan officer says, "We are very happy to have had your business, and this transaction has worked out very nicely, but we are a little puzzled. While you were away, we checked you out and found that you are a multimillionaire. What puzzles us is: why would you bother to borrow $5,000?"

The man smiled. "Where else could I park my Rolls-Royce in Manhattan for two weeks and pay only $15.40?"