That is a Cholla with no roots. You can grow new Cholla from the arms. Cut some healthy pieces off, let them sit in a shady place for a week or so, then plant them in some cactus soil with added perlite. Keep the soil barely damp. A cactus without roots can't use the water but, you have to offer a little encouragement so it will grow roots.
Use you spaghetti tongs and a very sharp knife - you don't want to touch this cactus.