They are considered seraphrims officially, but the variance between traditional 'angels' and pop cultures is huge. So much has been altered for image and perception they arent really the same. I believe in the hierarchy, they rank at the top, just under god himself. As per your question regarding prayer to one, while i dont believe in that, the mentality is that yes they have limited ability to answer and help, much like saints and such. Surely if you could pray to lucifer, another seraphim, and he answer, you can do the sae to the others.