The european bank account numbers are often posted publicly. If you are a VAT payer, you're supposed to check that the account you send money to is registered with the business in the public registry. Otherwise you may be held liable for the receiver's tax fraud. Many companies also show them at their webpage to make it easier to get paid. See e.g. https://www.pre.cz/en/contacts/bank-details/
The account number should be just an ID, not authentication mechanism.
The account number should be just an ID, not authentication mechanism.