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@Velocio
In all gear design one of the gears should always be a prime number.
It means that the gears will wear evenly and that all teeth will have an equal distribution of contact with the other gear (or chain, or belt, etc).
This applies to everything: watches, cars, trains, heavy machinery, drills, etc.
If something has a gear, then one of the gears should have a prime number of teeth.
In bicycle drivetrains the gears should be co-prime, which means relatively prime. There's a wikipedia page on it: http://en.wikipedia.org/wiki/Coprime_integers
With a bicycle this is easily achieved by having one sprocket be a prime number, but can be achieved otherwise by using two non-primes that result in a co-prime.
The goal is to avoid an intersection of the numbers when plotted, which is demonstrated by this image from WIkipedia:
So yes... an odd number of teeth help, but much better is to achieve co-prime at minimum, and much simpler is just to make the rear sprocket have a prime number of teeth.