Logic Masters Deutschland e.V.

This is my first real puzzle! Hope you enjoy it :)

Rules:

Normal sudoku rules apply. (place a digit in each cell such that every column, row, and marked 3x3 box contain each digit exactly once)

For columns 1, 5, and 9, digits in column X index the column where X appears in that row. As an example, if r8c9 was a 3, r8c3 would be a 9.

Digits do not repeat in cages, and sum to the number in the top left. The unmarked cage sums to a prime number.

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Thank you Nebula for brainstorming with me, and thank you so so much Ambrose and DarthParadox for the testing feedback!