Trouble calculating the number of days between two dates.

Trouble calculating the number of days between two dates.

I have a last service field in a customer form.
Using a formula field I'm calculating zoho.currentdate minus the last service date. (This is a date field) / 1000 * 60 * 60 * 24
The result gives me 169.95833334.

I've changed it to a decimal field with a decimal length of zero (0). and get the same result. 169.95833334.

If I change the field to a number (no decimals) I get an error telling me the zoho.currentdate is a bigint and and Last Service date is a date field.

All I want to do is have a result as a whole number

How can I fix this?