05AB1E, 5 4 bytes

2(вO

Takes advantage of the fact that only 1 is truthy in 05AB1E.

Try it online or verify all test cases at once.

2(вO  # full program
   O  # push sum of...
  в   # list of base-10 values of base...
 (    # negative...
2     # literal....
  в   # digits of...
      # implicit input
      # implicit output

05AB1E, 5 4 bytes

Ties emanresu A's Vyxal answer for #1.

2(вO

Try it online!

2(вO  # full program
   O  # push sum of...
  в   # list of base-10 values of base...
 (    # negative...
2     # literal....
  в   # digits of...
      # implicit input
      # implicit output

05AB1E, 5 4 bytes

2(вO

Try it online!

2(вO  # full program
   O  # push sum of...
  в   # list of base-10 values of base...
 (    # negative...
2     # literal....
  в   # digits of...
      # implicit input
      # implicit output

05AB1E, 5 4 bytes

2(вO

Takes advantage of the fact that only 1 is truthy in 05AB1E.

Try it online or verify all test cases at once.

2(вO  # full program
   O  # push sum of...
  в   # list of base-10 values of base...
 (    # negative...
2     # literal....
  в   # digits of...
      # implicit input
      # implicit output

05AB1E, 5 4 bytes

2(вO

Try it online! Beats all other answers.

2(вO  # full program
   O  # push sum of...
  в   # list of base-10 values of base...
 (    # negative...
2     # literal....
  в   # digits of...
      # implicit input
      # implicit output

05AB1E, 5 4 bytes

2(вO

Try it online!

2(вO  # full program
   O  # push sum of...
  в   # list of base-10 values of base...
 (    # negative...
2     # literal....
  в   # digits of...
      # implicit input
      # implicit output