Is a record ID in Zoho Books always numeric?

Is a record ID in Zoho Books always numeric?

Hi Support Team,

For storing Zoho Books' contact, invoice and other record IDs in an external app, I wanted to know if the IDs are always numeric.
As far as I can see in Books, they are all numeric and while fetching a record via the Zoho Books API, passing an alphanumeric value as the ID returns an "Invalid URL passed" error. This seems to suggest that the ID is implemented to be numeric only.

Could you kindly clarify on this?

Regards.