More than just a number: in Chinese tradition
七十二 is a symbolic 'lots' — Confucius is said to have had 72 worthy disciples (
七十二贤人),
孙悟空 the Monkey King has
七十二变 (72 transformations), and
三十六行 'thirty-six trades' has its sister phrase
七十二行 'seventy-two trades' meaning every line of work.