How to determine number with same amount of odd and even divisors With given number N, how to determine first number after N with same amount of odd and even divisors?
For example if we have N=1, then next number we are searching for is : 
2
because divisors:
odd : 1
even : 2

I figured out that this special number can't be odd and obviously it can't be prime.
I can't find any formula for this or do i have just compute it one by one and check if it's this special number ? Obviously 1 and number itself is divisors of this number.
Cheers

For a given integer $n$, every divisor larger than $\sqrt{n}$ is paired with a divisor smaller than $\sqrt{n}$.  Use this to figure out a general principle.
