2. They're the primary maintainer of one of the largest programming languages.
3. They do tons of HR/ERP type software.
4. They have a supply chain division (my company is a direct competitor, and we have 2000 employees--it's a drop in the bucket, but a few thousand here, a few thousand there and it starts to add up. Afaik, their supply chain org is bigger than ours).
5. Other things I probably don't know about.
Many of these things come with swarms of consultants who implement the software for companies that don't have any internal technical competency, which swells the number of workers by a lot.
Don't get me wrong, I'm not remotely a fan, I like to quote Bryan Cantrill's rant. However, they do a lot of things.