I was messing around with command blocks and summoned two charged creepers. then I went into survival to see if i could kill them. they both began to ignite, and one exploded and the other, which was right next to it lived! I began to experiment and came to the conclusion, that if a creeper explodes, and a mob is at least 1 block away and there is a block in between it and the creeper it lives away it lives. I also noticed that the charged creepers have the same explosion radius as normal ones.