It is admittedly harder to explain how Sudoku doesn’t actually have anything to do with arithmetic when there are variants like this one which do. And this one has a lot of arithmetic.
Rules:
Normal Sudoku rules apply.
Numbers outside the grid are the sum of all digits along the indicated diagonal. Digits are allowed to repeat if allowed by other rules.
Estimated difficulty: 2 out of 5
Solve on SudokuPad