I suggest you double-check what you posted.
"SITENAME" VARCHAR2(100 BYTE),
"NETWORKID" VARCHAR2(10 BYTE),
You should NEVER create or alter objects in the SYS schema. Recreate that table in a user schema and drop the one in the SYS schema.
That is a proven way to cause database corruption and problems.
I recognized this issue as the CUSTOMERID has row entries with non-numeric values.
It is NOT possible for an Oracle column defined as NUMBER to contain data with 'non-numeric values'.
So that data could NOT have been loaded into that table; the BAD DATA can only exist in your merged csv file so you will either need to recreate that file or use an editor to remove the multiple header rows.
Since the bad data can NOT exist in that column in the table I'm not sure how posting in the SQL forum can help.
But if you do have a SQL question that is the forum to post it in.