CHECK CONSTRAINT of string to contain only digits. (Oracle SQL)

Question

I have a column, say PROD_NUM that contains a \'number\' that is left padded with zeros. For example 001004569. They are all nine characters long.

I do not use a num

Answer 1

Cast it to integer, cast it back to varchar, and check that it equals the original string?

Answer 2

Works in all versions:

TRANSLATE(PROD_NUM,'123456789','000000000') = '000000000'