What does alphanumeric mean regarding my medicare subscriber number?

Clarification.  Where are you trying to enter your Medicare subscriber number?

Where in the TurboTax program are you being asked for a Medicare Subscriber Number?

The current Medicare card uses a 11digit/alpha character member number.  This new number was issued to all Medicare recipients two or three years ago and all new Medicare recipients.

alphanumeric simply means your medicare number which consists both numbers and letters