The offer price of $170 per share represents a premium of about 5.7% to CoreSite's closing price on Nov. 9, when Reuters first reported talks of the deal.

Shares of CoreSite rose 2.1% to $170.25 in premarket trading.

The Denver-based company has more than 24 operating data center facilities in North America, leasing out space to companies that outsource some of their computing power. It started as a company of private equity firm Carlyle Group Inc and became publicly listed a decade ago.

The deal is expected to close by the end of this year.

J.P. Morgan was the lead financial adviser to American Tower, while Evercore served as CoreSite's financial adviser.

(Reporting by Chavi Mehta and Tiyashi Datta in Bengaluru; Editing by Aditya Soni)