NEW YORK — Apple is Wall Street’s all-time MVP —that’s Most Valuable Property.

On Monday, Apple’s surging stock propelled the company’s value to $623 billion, the world’s highest, ever. It beat the record for market capitalization set by Microsoft in the heady days of the Internet boom.

After a four-month dip, Apple’s stock has hit new highs recently because of optimism around what is believed to be the impending launch of the iPhone 5, and possibly a smaller, cheaper iPad. Apple has been the world’s most valuable company since the end of last year. It’s now worth 53 percent more than No. 2 Exxon Mobil. Apple’s stock hit $664.74 in midday trading before retreating slightly to $662.38.

Microsoft’s 1999 peak was $620.58 billion, according to Standard & Poor’s.

The comparison to Microsoft does not take inflation into account. In inflation-adjusted dollars, the software giant was worth about $850 billion on Dec. 30, 1999. Microsoft is now worth $257 billion.

Analysts believe Apple’s stock has room to grow. The average price target of 38 analysts polled by FactSet is $745.80.

Despite the surge, Apple’s stock is not particularly expensive compared to its earnings for the last twelve months. The company’s “price-to-earnings ratio” is 15.6, compared to 16.1 for the S&P 500 overall. That suggests investors, unlike analysts, don’t believe the company can grow its profits much from current levels.

By contrast, Microsoft had a price-to-earnings ratio of 83 at the peak. The stock was caught up in the Internet mania and investors believed it could boost its earnings massively.