Any ideas for a formula to check if a Document Number/ID field is a number? I want to exclude any results from a saved search if the document number contains letters or is blank

CASE WHEN {number} - 1 > 0 THEN 1 ELSE 0 END. is 1

Thanks! I had a datatype error so I added To_Number and that worked: CASE WHEN TO_NUMBER({number}) - 1 > 0 THEN 1 ELSE 0 END