Alphanumeric account numbers?

Alphanumeric account numbers?

I've been searching for an answer to this but haven't been able to find anything -

Is it possible the make account numbers alphanumeric? I am migrating my client list to Zoho and all the existing account numbers are in the format "abc123" and I would rather not have to rename them all. Also, the alpha part makes it easier to remember the client - the alpha part is the first three letters of the account name.

Any suggestions would be greatly appreciated.

Thanks!