'Number' in the Access table designer is a collection of data types, not a specific type itself - you need to look at the field properties below the field list to see what the actual type is.
Alternatively, you could look the field type up programmatically. Using Delphi and DAO the code would look like this:
uses
DAO_TLB; //may need importing first via Component|Import Component
procedure Foo;
var
Engine: DBEngine;
DB: Database;
Table: TableDef;
begin
Engine := CoDBEngine.Create;
DB := Engine.OpenDatabase('C:\Somewhere\Database.mdb',
{exclusively?}False, {read-only?}True, '');
Table := DB.TableDefs['MyTableName'];
case Table.Fields['MyFieldName'].Type_ of
dbBoolean: ;
dbByte: ;
dbInteger: ;
dbLong: ;
dbCurrency: ;
dbSingle: ;
dbDouble: ;
dbDate: ;
dbBinary: ;
dbText: ;
dbLongBinary: ;
dbMemo: ;
dbGUID: ;
dbBigInt: ;
dbVarBinary: ;
dbChar: ;
dbNumeric: ;
dbDecimal: ;
dbFloat: ;
dbTime: ;
dbTimeStamp: ;
end;
end;
I would assume the C#/ADO.NET equivalent would be similar-ish.