Four Long Islanders are among the world's 1,645 billionaires, according to a list released Monday by Forbes magazine.

Bill Gates, co-founder of the computer software giant Microsoft Corp. and a prominent philanthropist, regained the top spot, with a net worth estimated at $76 billion as of this month.

Gates dethroned Mexico's Carlos Slim Helu and his family, who had been No. 1 on the Forbes list for four years in a row. This year, the telecommunications mogul was No. 2, with a fortune valued at $72 billion. Gates has led the Forbes list of the global rich for 15 of the past 20 years.

Locally, the highest-ranking individual was again hedge-fund investor James Simons, 75, with a net worth of $12.5 billion, up $800 million from a year ago. The East Setauket resident ranked No. 88.

The United States continued to be home to more billionaires than anywhere else, 492 in all, followed by China and Russia.

After Gates, investor Warren Buffett of the conglomerate Berkshire Hathaway Inc. was the next American on the wealthiest list. He ranked No. 4 with a net worth of $58.2 billion.

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Facebook founder Mark Zuckerberg climbed 45 spots to No. 21 as his fortune rose to $28.5 billion, up from last year's $13.3 billion. Former New York City Mayor Michael Bloomberg, whose wealth stems from the Bloomberg financial information service, ranked No. 16. His net worth was $33 billion, a gain of $6 billion year over year.

The other Long Islanders on the list were:

Charles Dolan, 87, at No. 408; he and his family had a fortune valued at $3.7 billion, a gain of $600 million from last year. The Cove Neck resident founded Cablevision Systems Corp. of Bethpage, which owns Newsday.

Kenneth Langone, 78, was No. 764 with $2.3 billion, an increase of $400 million over the previous year. The Sands Point resident helped start the building supply retailer Home Depot.

Louis Bacon, 55, was No. 1,092 with $1.6 billion, a gain of $300 million from a year ago. The hedge fund investor lives in Oyster Bay.

These two billionaires are listed by Forbes as having their primary residences in Manhattan, but are registered to vote on Long Island:

Ira Rennert, 79, an investor, owns a large home in Sagaponack. He placed No. 234 with a net worth of $6 billion, down $500 million year over year.

Julian Robertson Jr., 82, a hedge fund investor who owns property in Locust Valley, ranked No. 506. His fortune was valued at $3.2 billion, up $400 million from a year ago.