THIRTY-FIVE million is a lot people. It happens to be the number of those collecting Social Security benefits right now because either they or someone in their family earned the right to the benefits. One hundred sixteen billion dollars is also something of a mind-blower. That is the approximate total in the Social Security Trust Funds. Over the next 20 years, a massive shift in the ratio of the working population to the elderly population will begin. How most effectively to ensure the financial stability of the trust funds as fewer workers pay in and more retirees take out benefits is a crucially important policy issue facing whoever is president next year.

It is disappointing to hear Gov. Reagan, who hopes to be that president, deal -- as though it disposed of the matter -- with the awful complexity of Social Security financing by viewing with alarm the fact that some prison inmates receive benefits. An ever-growing list of interviewers has been told by him that "Son of Sam," the barbarous convicted slayer from Yonkers, is receiving Social Security disability benefits.

This "Horrible Example" in fact leads you nowhere in the effort to deal with the Social Security problem. But, predictably, it has evoked a flurry of activity, including proposed bills and congressional investigations into the outrage of such people's living on federal munificence. But all of these discussions run into the fact, basic to Social Security, that the right to benefits is earned.And, once the right has been earned, it is difficult to establish an y constitutional grounds for taking it away. The question is not, to quote the Supreme Court's opinion in one such case, "whether or not [appellants] are good or bad men, nor is it whether we would grant them annuities if we had unfettered discretion in the matter."

In this instance, the question is also not how best to dispose of this catchy but really tiny issue in Social Security. It is how to persuade Gov. Reagan that people need to hear how he thinks about the true issues that a president faces. Even if he could change the Constitution on these questions -- which he can't -- and even if he could get the convict population automatically disqualified, it wouldn't even nudge the curves on the chart that Gov. Reagan should be thinking about. What would he do to guarantee the trust fund's stability in the years ahead?