Why I'm getting arithmetic overflow error when inserting bigint number to a bigint column?

Question

I'm trying to insert a number to a column. Column datatype is BIGINT and I'm pretty sure that my number doesn't exceed the max value of BIGINT but still I get

Msg 8115, Level 16, State 2, Line 40
Arithmetic overflow error converting expression to data type int.
The statement has been terminated.

My recent activity was I change the datatype of that column from INT to BIGINT. I think somewhere internally my column is still defined as INT.

Here is my script.

Insert into Customer(Cust_ID)
Select 2150000000

Column Cust_ID datatype is BIGINT in the designer. It is also the PRIMARY_KEY and many table reference it.

EDIT: Here are some of the migration scripts

DROP TABLE dbo.Customer
GO
EXECUTE sp_rename N'dbo.Tmp_Customer', N'Customer', 'OBJECT' 
GO

Answer 1

OK I already found the answer. My table has custom constraints which call scalar functions which requires an INT parameter.

Changing all those function's parameter to BIGINT solves the problem.