difference between cast as timestamp and to_timestamp

[Divya Gehlot]

Hi,
Below gives me different values
Query 1:
select CAST(1530601200049 AS TimeStamp) from (values(1));
EXPR$0
2018-07-03T07:00:00.049-05:00

Query 2:
select TO_TIMESTAMP(1530601200049) from (values(1));
Apache Drill
50472-10-26T11:00:49.000-05:00

Query 3 :
select TO_TIMESTAMP(1530601200049,'YYYY-MM-dd HH:mm:ss') from (values(1));
Error :
Apache Drill
org.apache.drill.common.exceptions.UserRemoteException: SYSTEM ERROR:
IllegalArgumentException: Invalid format: "1530601200049" is malformed at
"0049" [Error Id: 03ac470f-e959-41c4-beba-5f3827815709 on <node1>:31010]

Why get I different values?

Thanks,
Divya