NSNumber *myInt = [NSNumber numberWithInt:12];
CFNumberType numberType = CFNumberGetType((CFNumberRef)myInt);

// numberType will then be one of:

enum CFNumberType {
   kCFNumberSInt8Type = 1,
   kCFNumberSInt16Type = 2,
   kCFNumberSInt32Type = 3,
   kCFNumberSInt64Type = 4,
   kCFNumberFloat32Type = 5,
   kCFNumberFloat64Type = 6,
   kCFNumberCharType = 7,
   kCFNumberShortType = 8,
   kCFNumberIntType = 9,
   kCFNumberLongType = 10,
   kCFNumberLongLongType = 11,
   kCFNumberFloatType = 12,
   kCFNumberDoubleType = 13,
   kCFNumberCFIndexType = 14,
   kCFNumberNSIntegerType = 15,
   kCFNumberCGFloatType = 16,
   kCFNumberMaxType = 16
};
typedef enum CFNumberType CFNumberType;