WITH XMLNAMESPACES('http://schemas.xmlsoap.org/soap/envelope/' AS soap,
'https://temp.uri.com/Project/Object/Data' AS data,
'https://temp.uri.com/Mngmt/' AS mgmt)
SELECT
RequestXML.value('(/soap:Envelope/soap:Body/mgmt:PrintList/mgmt:Account/data:AccNumber)[1]',
'BIGINT') AS 'AccNumber'
FROM
[dbo].[Table1]