Issue 21
Crossnumber

Prize crossnumber, Issue 21

Can you solve it?

post

17 March 2025

Our original prize crossnumber is featured on pages 66 and 67 of Issue 21.

Rules

  • An over-zealous copy editor has ‘corrected’ this crossnumber. In the original puzzle, every clue was of the form a † bA or a † bD, where a and b are positive integers, and † is +, –, ÷, or × (and A and D stand for across or down); the copy editor then took every clue, calculated a † b, and replaced a † b with the result. For example, if a clue now reads ‘6A’, then the actual clue could be:
    • 0 + 6A,
    • 3 + 3A,
    • 12 – 6A,
    • 1 × 6A,
    • 2 × 3A,
    • 6 ÷ 1A,
    • 120 ÷ 20A,
    • or many other things…
  • There is only one solution to the completed crossnumber. Solvers may wish to use the OEIS, Python, a team of 300 volunteers with abacuses, etc to (for example) obtain a list of prime numbers, but no programming should be necessary to solve the puzzle. As usual, no entries begin with 0.
  • One randomly selected correct answer will win a £100 Maths Gear goody bag, including non-transitive dice, a Festival of the Spoken Nerd DVD, and much, much more. Three randomly selected runners up will win a Chalkdust T-shirt. Maths Gear is a website that sells nerdy things worldwide, with free UK shipping.
  • To enter, submit the sum of all the digits in the row marked by arrows using this form by 25 September 2025. Only one entry per person will be accepted. Winners will be notified by email and announced on our blog by 1 November 2025.

Crossnumber

Crossnumber #21, set by Humbug:

Across clues

  • 1. 997A. (3)
  • 3. 81A. (4)
  • 6. 1D. (5)
  • 9. 286A. (4)
  • 10. 16D. (3)
  • 11. 2A. (3)
  • 12. 6A. (4)
  • 13. 1D. (5)
  • 16. 16A. (4)
  • 18. 360D. (4)
  • 20. 2A. (4)
  • 22. 8A. (4)
  • 24. 15104D. (4)
  • 27. 4A. (4)
  • 29. 40A. (6)
  • 31. 30A. (5)
  • 33. 6A. (4)
  • 35. 4A. (4)
  • 37. 668997D. (5)
  • 40. 34459245389A. (6)
  • 43. 7A. (4)
  • 45. 4A. (4)
  • 46. 8A. (4)
  • 48. 6A. (4)
  • 51. 4A. (4)
  • 53. 5A. (4)
  • 55. 14750A. (5)
  • 57. 4A. (4)
  • 58. 56D. (3)
  • 59. 256D. (3)
  • 60. 2A. (4)
  • 61. 4A. (5)
  • 62. 5A. (4)
  • 63. 64D. (3)

Down clues

  • 1. 1D. (5)
  • 2. 6172344439D. (5)
  • 3. 3D. (4)
  • 4. 4D. (6)
  • 5. 81707A. (5)
  • 6. 3A. (4)
  • 7. 72D. (3)
  • 8. 60A. (3)
  • 14. 15094A. (4)
  • 15. 4D. (4)
  • 17. 5901148A. (4)
  • 19. 19893A. (4)
  • 21. 725D. (3)
  • 23. 23D. (4)
  • 25. 3038A. (4)
  • 26. 3661706D. (4)
  • 28. 1925D. (4)
  • 30. 1009262A. (4)
  • 31. 1061A. (4)
  • 32. 41A. (4)
  • 34. 7568A. (4)
  • 36. 11727A. (4)
  • 38. 6468D. (4)
  • 39. 705159A. (3)
  • 41. 2302929D. (4)
  • 42. 766A. (4)
  • 44. 584828A. (6)
  • 47. 47D. (5)
  • 49. 59921D. (5)
  • 50. 21D. (5)
  • 52. 52D. (4)
  • 54. 54D. (4)
  • 55. 98D. (3)
  • 56. 944D. (3)

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