You might think that the president of the United States gets the best medical attention anyone can receive. But you wouldn't get an agreement from Dr. Edward B. MacMahon, an orthopedic surgeon and amateur medical historian, and writer Leonard Curry. In a new book, "Medical Cover-Ups in the White House," to be published by Washington's Farragut Publishing Co., they contend that medical treatment for presidents through the years often "has ranged from questionable to downright incompetent." Maybe that's why someone at the White House, nearly a year ago, ordered a copy of the still-incomplete book. Now completed, a copy was delivered to the White House library Friday.

The writers say physicians for presidents Wilson, Harding and Franklin Roosevelt failed to diagnose their patients' obvious symptoms of chronic and serious illnesses. Presidential illnesses cause sticky political problems, and the writers say that if history is a guide, "when the president faces a serious health problem, the full truth will be kept from the public" and "even though a disability amendment has been added to the Constitution, cover-ups are still possible and a physically or mentally impaired chief executive can find ways to remain in office."

Out and About In a peculiar use of prayer, fundamentalist minister R.L. Hymers, who has prayed for the death of Supreme Court justices who support legalized abortion, asked his followers in Los Angeles Sunday to pray for the removal of ailing Justice Harry Blackmun "in any way that God sees fit." In a sermon to his Fundamentalist Baptist Tabernacle congregation, Hymers led prayers against Blackmun, the 78-year-old member of the court's more liberal wing who recently suffered a recurrence of prostate cancer. "I don't know if our prayers will be answered," he said. "The answer to that will come if he {Blackmun} dies in time for President Reagan to appoint someone who is capable of the job." Hymers originally made the statement to 250 members of his congregation, but obliged a late-arriving television news crew by repeating 10 minutes of his sermon ...

Ollie and the boys down at the NSC have made us conscious of covert operations. So much so that First Class Inc., the local organization that gives classes and lectures in nearly everything from antiquing to Chinese back-walking massage, has developed a lecture on "Careers in Covert Operations" taught by a real former CIA operative, David Atlee Phillips. The lecture, for a mere $17, promises "sincere, invaluable information on how to start and flourish in a career with any U.S. intelligence organization" ...

Rep. Gary Ackerman spent the past five months taking off 109 pounds and is so determined to keep it off that he's giving his clothes away to the homeless, partially to make certain he never wears them again. The Democratic congressman from central Queens, N.Y., weighed 283 pounds when he started his medically supervised liquid protein diet. The only solid food he tasted in the past five months was a small portion of matzo during Passover. Ackerman had his weigh-in Friday and celebrated the end of his liquid diet by eating his first solid meal in a Queens deli -- a bowl of matzo-ball soup and a chicken sandwich. He says he will donate his outsized clothing to a homeless group in Queens and to Mitch Snyder's CCNV shelter here. Ackerman was one of the congressmen who slept out a night on the heating grates this past winter with Snyder and actor Martin Sheen ...

If former president Jimmy Carter keeps up all his carpentry work, someone's going to check to see if he has a union card. He was out again yesterday in Charlotte, N.C., helping build houses for the needy for Habitat for Humanity, a nonprofit group he has worked with before in renovating housing in Chicago and New York City. His wife Rosalynn and their daughter Amy are joining in the week-long project, in which 14 houses will be completed. Carter said he was involved because "I don't think our president is doing enough to address the problems of the homeless" ...

Royal Watch: Prince Andrew and Fergie are nearing the end of their Canadian tour, but not before a visit to a gold mine in Yellowknife in the Northwest Territories. The duchess of York, who seems willing to try most anything, dressed in safety helmet, coveralls and muck-about boots before going 800 feet underground into the mine ...