Would you like to impress your friends, gain a reputation as an economic savant, get your picture in the newspaper, have lunch on The Washington Post at your favorite local restaurant and win a passel of (minimally) valuable prizes, all for the price of an 18-cent stamp?

You can achieve all that if you can predict which day the national debt will reach a historic landmark: $1,000,000,000,000.

The government's debt seems certain to top $1 trillion sometime this fall, probably within the next few weeks. But none of the government's experts has been able to say precisely when that will happen. So the Federal Report is asking its readers to make the prediction by entering our "Trillion Dollar Forecast" competition.

All you have to do is send in the entry blank above, or any reasonable facsimile, telling us what day you think the debt will go over the $1 trillion mark. In addition, be sure to answer the second question, which will serve as the tiebreaker: how large will the debt be (to the nearest million dollar) at the close of business on the day the figure tops a trillion?

When the Treasury Department, which tallies federal indebtedness each business day, reports that the trillion-dollar landmark has been reached, we'll determine which reader made the most accurate prediction. (Our official reference will be the figure for "Total subject to limit--Closing balance today" as reported in Table III-C of the Treasury's daily publication, "Daily Treasury Statement.")

The person who wins will be feted at a lunch with Post reporters and editors and receive a Washington Post book bag stuffed with Washington Post T shirts for the winner's immediate family.

If more than one reader predicts the day and the amount precisely, the winner will be the answer with the earliest postmark. To be eligible, entries must be postmarked by midnight on the day before the debt reaches $1 trillion. The contest is open to everyone except employes of the Treasury Department and The Washington Post.

The most important thing you have to know in making predictions about the national debt is that debt levels are hard to predict, because the debt does not fluctuate evenly day to day. Some days, when the government's redemption of old securities exceeds the total of its new issues, the debt figure drops. Over time, though, the debt increases. Since Jan. 1 it has risen $51.2 billion.

At the close of business Wednesday, the national debt stood at $982,455,000,000. When will it top a trillion? If you can tell us, you could win the Trillion Dollar Forecast contest.