The Pythagoreans were inordinately fond of the number 10. As the sum of 1+2+3+4 it could be represented by an equilateral triangle with one dot at its apex, two arranged symmetrically below it, three on the line below that and four on the base. And since one represented existence, two creation, three life, and four the elements (earth, air, fire and water) from which everything was believed to be made, 10 had the virtues of everything. And that explained (to the Pythagoreans at least) why man was created with 10 fingers and ten toes.
But there are more down-to-earth reasons for admiring the number 10, for 10 is the number of:
chromosomes of a greenfly;
heliports in the UK;
platforms at both Moorgate and Baker Street stations - the most on the London underground;
seconds duration of the average chimpanzee's act of sexual intercourse;
grams of salt we eat on average every day;
vowels in the Korean alphabet.
pounds you need to tender to receive a penny change when buying `The Book of Numbers' by William Hartston (Richard Cohen Books).