How can I convert Bigint value which produced with Timespan?

CREATE TABLE Timing (
        StartTime DATETIME
        ,EndTime DATETIME
        ,ResultTime BIGINT
        ,ElapsedTime VARCHAR(20)
        )

insert into Timing (StartTIme, endtime) values
('2014-11-20 14:35:42','2014-11-28 14:36:15')

DECLARE @MyNullTime TIME
SET @MyNullTime = '00:00:00'

SELECT StartTime,EndTime
        ,DATEDIFF(MILLISECOND, starttime, EndTime) AS 'tResultTime (MS)'
        ,cast(DATEDIFF(HOUR, starttime, EndTime) / 24 AS VARCHAR(5)) + 'day(s) ' 
        + cast(DATEADD(SECOND, - DATEDIFF(SECOND, EndTime, StartTime), @MyNullTime) AS VARCHAR(8)) AS 'Elapsed Time'
FROM timing

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-Vaibhav Chaudhari