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Question

Out of the four numbers listed, three are alike in some manner and one is different. Select the odd one.

2126, 9819, 7568, 8423

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
8423

Odd One Out Number Analysis

The task is to identify the number that is different from the others among the given set: 2126, 9819, 7568, and 8423. Three numbers share a common characteristic, while one does not.

Reasoning for Difference

We examine the properties of each number to find the pattern:

  • 2126: This is an even number, divisible by 2. Its prime factorization is $2 \times 1063$. It is a composite number.
  • 9819: The sum of its digits is $9 + 8 + 1 + 9 = 27$. Since 27 is divisible by 3, 9819 is divisible by 3 ($3 \times 3273$). It is a composite number.
  • 7568: This is an even number, divisible by 2. Its prime factorization is $2^4 \times 11 \times 43$. It is a composite number.
  • 8423: This number is odd. Upon checking divisibility by small prime numbers, it is found that 8423 has no prime factors other than 1 and itself. Thus, 8423 is a prime number.

Identifying the Unique Number

The numbers 2126, 9819, and 7568 are all composite numbers.

The number 8423 stands out as it is a prime number.

Therefore, 8423 is the odd one out.

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Similar Questions

  1. Based on the English alphabetical order, three of the following four letter-cluster pairs are alike in a certain way and thus form a group. Which letter-cluster pair DOES NOT belong to that group?
    (Note: The odd one out is not based on the number of consonants/vowels or their position in the letter-cluster.)
  2. Based on the English alphabetical order, three of the following four letter-clusters are alike in a certain way and thus form a group. Which letter-cluster DOES NOT belong to that group?
    (Note: The odd one out is not based on the number of consonants/vowels or their position in the letter-cluster.)
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Important Questions from Classification

  1. In the following question, four number pairs are given. In each pair the number on left side of (-) is related to the number of the right side of (-) with some Logic/Rule/Relation. Three pairs are similar on basis of same Logic/Rule/Relation.
    Select the odd one out from the given alternatives. (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 /subtracting /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)

  2. Three of the following four are alike in a certain way and thus form a group. Which is the one that does NOT belong to that group?
    (Note: The odd one out is not based on the number of consonants/vowels or their position in the letter cluster.)

  3. 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 their 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.)

  4. The following contains two pairs of words which are related to each other in a certain way. Three of the following four word-pairs are alike as these have the same relationship and thus form a group. Which word-pair does NOT belong to that group?
    (The words must be considered as meaningful English words and must not be grouped based on the number of letters/number of consonants/vowels in the word)

  5. Three of the following four options are alike in a certain way and thus form a group. Which is the one that does NOT belong to that group?

    (NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into their constituent digits. E.g., 13 – Operations on 13 such as adding/subtracting/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.)

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