Yep, thats right. Thanatophobia is the fear of death. I looked up the number of christians and muslims, and it's 3.6 billion. So 2.1 billion people are christian, and 1.5 billion people are muslims, I say this because these people all affirm to some kind of afterlife. So thats some ammo you can use against theists. Ask them if there afraid of death, and if they say yes then tell them that they have thanatophobia. This number could also be a little higher if you ran into some hindus or other people that affirm to some kind of afterlife.