Three of the following numbers are alike in a certain way and one is different. Pick the odd one out. (NOTE : Operations should be performed on the whole numbers, without breaking down the numbers into its constituent digits. E.g. 13 – Operations on 13 such as adding /deleting /multiplying etc. to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.

Correct option is D

We can check whether each number is prime, divisible by a certain number, or follows a specific mathematical rule without breaking down into individual digits.
829 – This is a prime number.
643 – This is also a prime number.
821 – This is a prime number.
237 – This is also not a prime number (it’s divisible by 3).
Analysis
 Among these, 237 is the only non-prime number in the options that does not exhibit the divisibility rule as clearly.