> The account number is literally on the bottom of your checks. It's not a secret and shouldn't be treated as one. Both parts of your second sentence are true,

> The account number is literally on the bottom of your checks. It's not a secret and shouldn't be treated as one. Both parts of your second sentence are true, but, I think, irrelevant in practice: much like the SSN, which isn't meant for and shouldn't be used for identification but nonetheless is, the account number shouldn't be treated as a secret but is, in the sense that banks permit withdrawal activity on the basis of just the account number. They shouldn't! But they do.