What number doesn’t belong with the others

I don't think that 144 belongs because it is an outliar, meaning that it is at a much larger number than the others.

I don't think that 81 belongs because all of the other numbers end in even numbers.

I dont' think that 64 belongs because both of the numbers are even in 81, and 32 there is one odd and one even. In 144 there are two even but there is still an odd number.

I don't think that 32 belongs because it is half of 64. 81 is not half of 144 and 64 is not half of 81. So, this is different.

32 was the hardest.

ratio is 2 : 9

the answer is three

13.5 : 3