Shares of Apple, the world's most valuable technology company, hit the $500 mark Monday, valuing the company at $468.6 billion.

At that level, Apple easily also maintains its lead as the world's most valuable company. ExxonMobil, the biggest U.S. energy company, is No. 2, with a value of only $398.5 billion.

At midday, Apple shares had fallen slightly, to $499.54, up $6.12, but they recovered to close at $502.60. up $9.02. Their Monday high was a record $503.83.

Apple, based in Cupertino, Calif., first overtook ExxonMobil, based in Houston, as the world's most valuable company briefly last August.  Subsequently, shares of Apple dipped in October after reporting lower-than-expected fourth-quarter results.

Shares of Apple opened at $499.86, after closing Friday at $493.42. They quickly topped $500 and were trading above $502, or up about 2 percent, after the first three minutes of trading. U.S. markets generally rose after the Greek Parliament ratified austerity measures demanded by the European Union.

The latest activity brings the total return on Apple shares above 40 percent for the past year, which included the Oct. 5 death of Chairman Steve Jobs. The shares have been on a tear since the company's first-quarter results surpassed analyst estimates for both earnings and revenue growth. New CEO Tim Cook predicted continued strong sales of Macs, iPods, iPads, iPhones and entertainment services.

Meanwhile, speculation about new Apple products, especially the long-awaited successor to the two-year-old iPad2, perhaps the iPad3, have sent the shares on a tear the past three weeks.

Apple shares have gained 24 percent since Jan. 3, including an 8 percent leap in the past five days.

Shares priced at $500 and above are rare but not unusual. Warren E. Buffett's investment vehicle, Berkshire Hathaway, based in Omaha, Neb., traded at $118,770 Monday. In 2009, Berkshire decided to classify those as "A" shares and issued a new class of lower-priced "B" shares to make them more affordable to small investors. Berkshire Hathaway "B" shares traded at $79.33.

Apple was founded on April 1, 1976 but only incorporated on Jan. 3, 1977.  Known then as Apple Computer, the company's initial public offering was priced at $22 on Dec. 12, 1980. The shares have split three times, so that on an adjusted basis, the IPO price would now be viewed as $2.75.

Over the past 52 weeks, Apple shares have risen nearly 41 percent.