The Apple corporation is Wall Street's all-time most valuable property.

Apple's surging stock last night propelled the company's value to $624 billion, the world's highest, ever.

It beat the record for market capitalisation 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 is now worth 54% more than number two Exxon Mobil Corp.

Apple's stock closed at $665.15 last night up $17.04, or 2.6%, from Friday's close. Microsoft's 1999 peak was $620.58 billion, according to Standard & Poor's.

But the comparison to Microsoft does not take inflation into account. In inflation-adjusted dollars, the software giant was worth about $850 billion on December 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, do not believe the company can grow its profits much from current levels.

Microsoft had a price-to-earnings ratio of 83 at the 1999 peak. The stock was caught up in the Internet mania of the time and investors believed it could boost its future earnings massively.

Analysts believe the launch of a new iPhone in a month or two will be Apple's biggest product introduction yet.

They also speculate that a "mini iPad," could expand the number of people who can afford one of Apple's tablets. The cheapest iPad cost $399, compared to $199 for the latest Google and Amazon tablets.

Analysts are speculating - based on rumours - that Apple plans to make a TV set to complete its suite of consumer electronics products. Apple usually does not comment on its future product plans until a few weeks or days before a launch.

By coincidence, the peak price for one Apple share is now less than $2 away from the retail price of the Apple I computer in 1976. It sold for $666.66.