Given a number, print out its "collective sum"
05AB1E, &nbsp;4&nbsp; 3 bytes

-1 thanks to Kevin Cruijssen (use of € avoiding a })

€£O


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How?

€£O - implicit input   e.g. 2315
€   - map with:
 £  -   head to             23, 231, 2, 2315
  O - sum                   2571