Question on Order # generation

[galaxy]

I see when an order is generated it is in the form: Order #613a70610e4f0

What exactly is that number?  It looks random.  I cannot find it anywhere in the admin section (but see the open invoice it refers to without any reference to that number).  So when someone calls asking about that order number, where do I look?  Wouldn't it be better to reference the invoice number?

[galaxy]

Found it.  Had to run cron, then it appears in the approval queue on the billing overview page.

Was not mentioned in the documentation when I looked for it.