Find the dissimilar number from the following:
16, 256, 64, 624, 1024

Let's check the mathematical properties of each number:
* $16=4^2=2^4$
* $64=8^2=2^6$
* $256=16^2=2^8$
* $1024=32^2=2^{10}$

All these numbers ($16,64,256,1024$) are perfect squares and also exact powers of 2.
However, $624$ is not a perfect square ($25^2=625$). Therefore, $624$ is the dissimilar (odd) number.