Step 1: The 'xa' in the names of apixaban and rivaroxaban hints directly at factor Xa.
Step 2: Apixaban binds the active site of factor Xa without needing antithrombin as a cofactor, hence 'direct' Xa inhibition.
Step 3: By halting Xa it stops thrombin generation, which is why it prevents and treats venous thromboembolic disease such as DVT and PE.
Step 4: It is therefore not an antithrombin-dependent agent, not a platelet activator, and certainly not a clotting factor itself.
\[\boxed{\text{Direct factor Xa inhibitor}}\]