Classification Choose Odd Numbers

125 is the number in the group which is a perfect cube.

Each of the numbers except 27, is a prime number.

Each of the numbers except 257, is one less than the square of a certain number.

Each of the numbers except 380, is either one less or one more than the square of a certain number.

49 is the only perfect square number in the group.

All other numbers are cubes of odd numbers.

All other numbers are cubes of odd numbers.

Here logic is:

13 = 1 + 3 = 4 → Even number

17 = 1 + 7 = 8 → Even number

23 = 2 + 3 = 5 → Odd number

37 = 3 + 7 = 10 → Even number

73 = 7 + 3 = 10 → Even number

Hence, '23' is the correct answer.

131 is the only prime number in the group.

Each of the numbers except 399, is one more than the square of a certain number.