(Note: This appendix is very much under development. Check back periodically.)
It may seem silly to devote space to numbers as physicists by hypothesis love numbers, but the standard undergraduate training of physicists does not include a course in number theory per se, so most of what they are likely to know is gleaned from at most one course in complex numbers (math double majors and math minors excepted). This chapter makes no attempt to present an exhaustive review of number theory (however cool and worthy of a deeper treatment it might be) but instead confines itself to just a few points of direct relevance to electrodynamics.