apache2 is a meta package that just selects other packages. If you installed apache by installing that package, you just need to run this to clean up the automatically selected packages:
sudo apt autoremove
If that doesn't work, you might have installed one of the dependents manually. You can target all the apache2- packages from space and nuke the lot:
sudo apt remove apache2.*
For future reference, to find out which package a binary is from, you can run this:
dpkg -S `which apache2`
I'd expect that to come back with apache2.2-bin (at the time of writing).