Oracle Corp., the world’s second-largest software maker, agreed to buy RightNow Technologies Inc. for $1.5 billion, gaining customer-service expertise to bolster a new Internet-based product, Bloomberg reported.

RightNow investors will get $43 a share, Oracle said today in a statement. That’s 20 percent more than RightNow’s closing price on Oct. 21.

The acquisition will add software that helps companies serve customers using call centers, the Internet and social networks. Oracle is making its biggest purchase since Sun Microsystems Inc. last year after introducing the Oracle Public Cloud, which delivers software online via cloud computing, to spur demand for its programs.

“Oracle is getting serious about its own cloud,” said Richard Williams, an analyst at Cross Research. “This is the first infrastructure buy, and it means they’re putting the plumbing for the cloud together.”

The acquisition values RightNow at 68 times earnings before interest, taxes, depreciation and amortization, the highest multiple of similar deals in the United States in the past five years, according to Bloomberg data. Since 2006, the median ratio of six enterprise software and service deals of more than $1 billion was 17 times earnings.