NumbersThese brain teasers rely on your ability to recognize groups of common attributes. For each of these puzzles you'll need to figure out why the words or letters are grouped as they are. Sometimes you will be asked to pick the odd-one-out or to place a new word into the correct group.
Which number doesn't belong?
HintRemember your math.
Answer51 does not belong because it is the only number that is not prime.
A prime number has only itself and 1 as factors. 51 has 4 factors: 1, 3, 17, and 51.
See another brain teaser just like this one...
Or, just get a random brain teaser
If you become a registered user you can vote on this brain teaser, keep track of
which ones you have seen, and even make your own.
Back to Top