Simply put, no they’re not. An Australian Company Number (ACN) is a nine-digit number which is issued by Australian Securities & Investments Commission (ASIC) when a company is registered. This number is an identifier purely for companies, & is issued immediately once approved by ASIC. After company registration, you can then apply for an ABN.
An Australian Business Number (ABN) is an eleven-digit number issued by the Australian Business Registry (ABR), a branch of the ATO. This number is given to all entities carrying on a business, doesn’t cost you to get one, & is issued immediately provided all of the information on your application is true & correct.
You can register for a business name at the same time as your ABN application. If you choose not to register for both at the same time you will need to go to the Australian Securities and Investments Commission (ASIC) to register your business name. You can do this after you get your ABN. The fee for business name registration is $35 for one year or $82 for three years.