We photograph with top-of-the-line Canon and Nikon Cameras and lenses. This means that the images are of the highest quality and resolution. For the techinical answer, the files when saved are 4500-5500 pixels for the largest edge. We save everything full-res jpeg at 300 dpi. The cameras range from 16-28 megapixels as of this writing. The end result is that you are able to enlarge the images as large as you want, and the quality will be top notch.
Much like a brain, a larger amount of megapixels doesn't always mean a smarter system ;) For example, there are 40 megapixel phones out now, but the resulting images would not print nearly as well as an image from a 16 megapixel professional camera. We always evolve to take advantage of the latest technology, but megapixels are only one factor in a much larger process.