Except '841', all are even numbers.
All others are divisible by 13.
In all other options, digit at the second place is the difference from first and third digits.
Except '87', all a prime numbers 87 is divisible by 3.
Except '64', none of the numbers is a square or a cube.
Only 75 is divisible by 15.
In all other options, sum of the digits is 20.
3216 ? 3 + 2 + 6 - 1 = 10;
2338 ? 2 + 3 + 8 - 3 = 10;
3205 ? 3 + 2 + 5 - 0 = 10;
2015 ? 2 + 0 + 5 - 1 = 6
Therefore, 2015is different from the other three.
In all other options, digit in the middle is the sum of the other two digits.
All others are complete squares.
This is the only non-square number in the group.
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