Multiple choice general knowledge math & puzzles

In the below Question, 5 numbers are given. Out of these 4 are alike in certain way but the rest 1 is different.

  1. 21

  2. 69

  3. 81

  4. 83
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

21, 69, and 81 are composite numbers. 83 is a prime number, making it the odd one out.

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