What do Walgreens, Intel, Walmart, and American Express have in common? According to an analysis of Fortune 100 companies compiled by PRWeek on July 26, each has a Facebook page, Twitter handle, and Foursquare account, aggregating millions of followers and “likes.”

Coca-Cola tops the charts with just over 33 million total fans, followed by Walt Disney with 28 million, and Walmart is third with nearly 8 million. Interestingly—but perhaps not surprisingly—Apple has no engagement on any platform.

The ability to boast ...