how to handle the Numeric datatype = datetime in the where clause

In a where clause, I need to put billing_period = effective_date. The billing_period is numeric(6,0) while the effective_date is datetime. I’ve come up with the following code.

Step 1 is to convert billing_period into varchcar

Step 2 is to convert effective_date into varchar. This step requires peeling each part from the date type and padding the month and day.

cast(rut.BILLING_PERIOD as varchar(6))+'01' =
cast(datepart(yy,b.effective_date) as varchar(4))+
REPLICATE('0',2-len(cast(DATepart(mm,b.effective_date) as varchar(2))))+cast(DATepart(mm,b.effective_date) as varchar(2))+
REPLICATE('0',2-len(cast(DATepart(dd,b.effective_date) as varchar(2))))+cast(DATEPART(dd,b.effective_date) as varchar(2))