title: How to make short account number
body: <p>I have project and every user has own account number. The problem is account numbers is 7 digits (from 1000000 to 9999999) and i want them to 5 digits (easy to remember and payment companies). 
  I know internet provider they have around 3 million users but they give 5 digit account number, how? Is there any way?</p>