I am switching phones from verizon to virgin mobile is there anyway to keep my old phone running?

I have a samsung juke and am getting a new X -Tc from virgin mobile.I Buy Xenical pills want to keep my old number when I switch.But my mom wants my old phone.Is there any way I can keep my old number and get a number for my old phone ? So that my mother can use it? My phone is a prepaid by the way.