if (LEN(@SerialNo) > 15)
BEGIN

DECLARE @NumberToConvert VARBINARY(MAX)

-- Convert the number into reverse HEX
SET @NumberToConvert =  CONVERT(VARBINARY(max), REVERSE(CONVERT(VARBINARY(max), CONVERT(VARBINARY(MAX), CONVERT(BIGINT, @SerialNo), 1))))
select @NumberToConvert

-- Chop off last 2 hex numbers (as 00 from 0x00 was placed at end and we do not need) and revert back to varchar into main variable
SET @SerialNO = CONVERT(varchar(MAX), CONVERT(bigint, CONVERT(VARBINARY(MAX), LEFT(cast(CONVERT(varchar(MAX), @NumberToConvert, 1) as varchar(32)),len(CONVERT(varchar(MAX), @NumberToConvert, 1)) - 2), 1)))
select @SerialNo

END