This puzzle is simultaneously a gridless crossword and a Sudoku puzzle. The grid can be filled in with numbers in a unique way subject to the following conditions:
It is a valid Sudoku grid (all rows, all columns, and all blocks of 9 squares having each number 1 through 9 exactly once)
AND
It is a valid crossword if you read off the numbers using T9 (2 = [abc], 3 = [def], ... 9 = [wxyz]) as in a text message. The 1's form the filled in blocks for the crossword. Notice that a 2 can be read as an "a" going across, but a "c" going down. As any gridless crossword should, it has standard crossword symmetry.
The four 7-number answers are all real phone numbers. If you plug them into the formula in the bottom you get 6294686 which is T9 for MAXIMUM (and no other word in the O.E.D.).
The title is Sudoku in T9.
The final grid is:
237648591 598731264 461259873 325874916 674912385 819563742 752496138 943185627 186327459
The across answers are:
1. adroitly
9. kyuse
10. ami
12. io
13. alwtse
15. 3258749
17. o
18. orgy
19. cfuk
21. u
22. 9563742
23. slagyo
26. et
27. wie
28. ulnar
30. uneasily
The down answers are:
1. clientry
2. exmap
3. st
4. 6728954
5. help
6. t
7. katzdr
8. wop
11. idolatry
14. 9423657
16. lizceo
20. tidal
23. nyuc
25. lit
29. ni
31. f
2006 MIT Mystery Hunt