Google Sheets VLOOKUP

VLOOKUP doesn't seem to work when the search key is numeric and all the values in the range are also numeric. Even if the key is a quoted numeric string eg "603".

I find I can get round this by adding "" to the key, eg VLOOKUP("603"+"", Db, 4, 0). Presumably this coerces the search comparison to work in string terms.

Also NB that if a key range is sorted with numbers first, eg {118, 151, "AB"}, vlookup won't work properly unless you set the is_sorted param to 0.