OK - without looking anything up - I also think the answer is 26! - unless I'm missing something????
So are you suggestion that there are a finite set of humans born to the World? - but then there is the nature Vs nurture thing to complicate matters to make a World full of billions of wonderful individualists (except for me

)
PS 26! = 4,032,914,611,266,056,355,840,000 - which is more than the Worlds population