Is there a way to customize the "account number" field in "accounts" to accept alphanumeric input?

Is there a way to customize the "account number" field in "accounts" to accept alphanumeric input?

My company issues alphanumeric account numbers.  Rather than try to get a Fortune 200 company to overhaul their system, I was hoping for a way to get Zoho to accept letters, not just numbers.  Any ideas?