President Reagan said yesterday that he has consulted frequently with former president Richard M. Nixon as he prepares for November's summit meeting in which he wants to "try to find a way to deal practically" with the Soviet Union despite "great differences" between the superpowers.

Responding to a question at a luncheon with journalists, Reagan praised Nixon as "most knowledgeable on international affairs."

While Nixon had one Soviet leader to deal with during his presidency, Leonid Brezhnev, "My problem for the first few years was they kept dying on me," Reagan said. Three Soviet leaders, including Brezhnev, have died since Reagan took office in 1981. The Nov. 19-20 meeting with Mikhail Gorbachev in Geneva is Reagan's first with a Soviet leader.

When asked about his hopes for the meeting, Reagan said, "What we hope to do is make them recognize that we both have to live in the world together and it doesn't mean we have to love each other or that we have to change each other's system."

Nixon was consulted by Reagan in advance of his meeting last year with then-Soviet Foreign Minister Andrei Gromyko, and the former president, the first to resign from office, was also consulted frequently by Reagan aides during the 1984 campaign.

A source familiar with Nixon's recent White House contacts said the former president has had "infrequent" conversations since last year, and all contacts have been initiated by Reagan or advisers, usually chief of staff Donald T. Regan or Secretary of State George P. Shultz.

Reagan said yesterday "there are great differences" between the U.S. and Soviet systems. "And they're not going to like ours; we don't like theirs. But we have to live in a world together. And I think one line recently written by President Nixon was very true. He said of our country, 'We want peace.' He said the Soviet Union 'needs peace.' And they do with that great massive buildup, the greatest the world has ever seen in military might . . . ."

Reagan's admiration for Nixon's views on the Soviets is a new development. In challenging incumbent Gerald R. Ford during the 1976 GOP primaries, Reagan was sharply critical of the Nixon-Ford-era policy of "detente" toward Moscow, and specifically attacked former secretary of state Henry A. Kissinger.

Nixon recently wrote an essay on the summit in Foreign Affairs, some of which has apparently been incorporated in Reagan's recent comments. For example, Nixon said the summit agenda should deal with "potential flash points for U.S.-Soviet conflicts" before it addresses arms control issues. Reagan made a similar point in an interview with college students last week.

Other advice from Nixon has not been accepted in the White House. He suggested that human rights issues should be dealt with privately, while Reagan has made them a highly visible aspect of his approach to Moscow.

Nixon said possible deployment of Reagan's "Star Wars" missile defense system, at least in a limited fashion to protect U.S. silos, is "the ultimate bargaining chip" in negotiations with the Soviets over deep cuts in Moscow's offensive missile forces. Reagan has said Star Wars is not a bargaining chip.

In the session yesterday, Reagan also repeated his opposition to protectionist trade bills in Congress, suggesting that the loss of many jobs in U.S. industry was not because of imports but modernization.

On another topic, Reagan said in an interview with the Spanish Information Network that was released yesterday that anti-Sandinista rebels in Nicaragua have reached 20,000 and are getting stronger. He said members of Congress who had opposed his request for aid to the rebels were suffering from a "Vietnam syndrome," or fear of U.S. military involvement.