Do dark matter interact with itself

If so, why does it not clump up like galaxies?

Also, if they do not interact with itself or regular matter, what keeps it around the galaxies?

The words "dark matter" are just place holders. That means that scientists have no idea what it is, how it effects us, or how it interacts, etc... For all that it matters, they could called it "Bob" or "aslgfnlajsglblknsl". That still doesn't mean that they know what it is. Its the same thing with "dark energy".