If you mean to do this in a microflow, then yes:
formatDateTime($someDateVariable, ‘w’)
See https://docs.mendix.com/refguide/parse-and-format-date-function-calls
If you mean in the domain definition, then yes but only as a calculated value. You will need to connect a microflow to do this.
But if you want to select objects and restrict to a dateattribute being a certain weeknumber, than in the retrieve-activity use the function week-from-datetime: