An alternative (simply a refactor):
DECLARE @v-2 VARCHAR(1000)
SET @v-2 = '2,22,5,1,88,2000,7897,800'
SELECT CAST( x.query('fn:min(number)') AS varchar),
CAST( x.query('fn:max(number)') AS varchar),
CAST( x.query('fn:count(number)') AS varchar)
FROM
(
SELECT CAST('<number>' + REPLACE(@v,',','</number><number>') + '</number>' AS XML) AS X
) s