There are, so far as I'm aware, two ways to qualify for the [Epic] tag on epic feats:
1. Having 21 HD or more (being a level 21 character, you would have 21 or more HD)
2. Being a True Dragon of at least Old age (according to Draconomicon, the fact all published True Dragons already have more than 21HD by that age doesn't seem to matter).
The only other way you can get an Epic feat is by having at least 11 levels of Ranger, and that only lets you nab Uncanny Accuracy, not any other feat.