Apple is the world’s most valuable company, ever.

On Monday, its surging stock propelled the company’s value to $621 billion, beating the record for market capitalization set by Microsoft Corp. in the heady days of the Internet boom.

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 Inc. 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 Corp.

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.