Sudoku puzzles are incredibly popular with mathematicians and nonmathematicians alike. However once you have solved a few of them, or even written a program to solve them for you, then can become tedious.
But this does not mean an end to writing digits in boxes: as this blog post will reveal, there are a great number of other puzzles which revolve around arranging digits correctly.
3×3 Grids
The aim of all the puzzles in this section is to place the digits 1 to 9 in the boxes in order to make certain types of number in each row and column.
Puzzle #1



even 



prime 



cube 
prime 
cube 
prime 

In this first puzzle, place the digits 1 to 9 in the boxes so that the three digit numbers in the first, second and third rows are even, prime and cube respectively and the three digit numbers in the first, second and third columns are prime, cube and prime respectively. 
Of course many more puzzles of this type can be created. Here are a few I have designed:
Puzzle #2



emirp* 



even 



emirp* 
emirp* 
odd 
square 
*An emirp number is a prime number which is a different prime number when the digits are reversed.
Puzzle #3



multiple of 17 



multiple of 25 



multiple of 9 
multiple of 11 
multiple of 16 
multiple of 12 
Puzzle #4



prime 



prime 



prime 
prime 
square 
prime 
2×2 Grids
Of course, there is no need to restrict this type of puzzle to 3×3 grids. Here are some puzzles on 2×2 grids:
Puzzle #5


prime 


multiple of 8 
prime 
multiple of 4 

Can you place the digits 1, 2, 3 and 4 in this grid so that all the two digit numbers formed have the required properties? 
Puzzle #6

Can you place the digits 1, 3, 5 and 7 in this grid so that all the two digit numbers formed are prime? 
Puzzle #7

Can you place four different digits from 1 to 9 in this grid so that all the two digit numbers formed are prime? How many ways can this be done? 
And Finally…
Similar puzzles can be formed from nonsquare grids, like these:
Puzzle #8



prime 



prime 
prime 
prime 
prime 

Can you place the digits 1, 3, 5, 7 and 9 in this grid so that all the numbers formed are prime? 
Puzzle #9




prime 




prime 
prime 
prime 
prime 
prime 

Can you place the digits 1 to 7 in this grid so that all the numbers formed are prime? 
The answers to the puzzles in this post will be appear here from Sunday 19th July at midday. If you have enjoyed these puzzles, why not try putting some more digits in boxes in our £100 prize crossnumber.
Matthew is a postdoctoral researcher at the University of Cambridge. He hasn’t had time to play Klax since the noughties, but he’s pretty sure that Coke is it!
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