41 is a good (somewhat totally random) number for this class, but can't be reused again and again... this is the pattern applied in appache commons HashCode based on Effective Java by Joshua Bloch. You can basically take 2 prime number then do the same-ish pattern that you've done for each different class that you want to implement hashcode and it will be fine. 

41 is just not a magic number coming from nowhere... like 17 and 37 in the apache commons library; http://commons.apache.org/proper/commons-lang//apidocs/org/apache/commons/lang3/builder/HashCodeBuilder.html