This mental magic trick is an amazing illusion of superhuman memorization and mathematical calculations. It is as close to pure magic as you could ever imagine! It requires no set-up, no special props, no gimmicks, and no accomplices.
There is nothing to hide, no misdirection, and no sleight of hand. The performer can perform the trick at a moment's notice without any preparation.
It can be performed for one person, a small group, or before a large audience.
Because the performer does the entire trick mentally, there is virtually no way that a spectator can detect exactly how this trick is done.
Although the trick is done mentally, there is a trick. The mental part appears to be very difficult but, because of a trick that only the performer knows, it is actually much, much easier than it appears.