http://en.wikipedia.org/wiki/7744_(number) http://en.wikipedia.org/wiki/7744_(number) Which also says "There are also very few squares with no unpaired digits"

http://en.wikipedia.org/wiki/7744_(number) http://en.wikipedia.org/wiki/7744_(number) Which also says "There are also very few squares with no unpaired digits", so the 'only number' bit seems erroneous (it did sound hard to believe).