If we've guessed that the number will be in the mid to high 20s, then 27 is the only number one could logically arrive at. 24, 25, 26, and 28 are easy to elimin

If we've guessed that the number will be in the mid to high 20s, then 27 is the only number one could logically arrive at. 24, 25, 26, and 28 are easy to eliminate because 19,863 is neither an even number nor a multiple of 5. That's all there is to it.