They have reddish stripes to mark off every ten feet (as in pedes, not 12 inches). Their shell looks hard as armor, and tough to break.
Centipedes are hairy wider creatures that are soft in comparison. They actually look a lot creepier, and have only around 30 or 34 feet compared to the millipede’s nearly 80 by my count. Also centipedes can bite. Millipedes just give off an ugly smell as self defense, or they roll into a ball so that you can’t pick them up or hurt them.