Each square of the 5x5 grid below contains a number 1-25. Divide the grid into five regions so that the number of squares and the sum of the squares in each region are both odd prime numbers. (1 is not a prime)
For example, the region consisting of {2,3,8} is a valid region. It contains 3 squares (3 is an odd prime) and the sum of the numbers in the squares is prime (2+3+8=13 is an odd prime).
+--+--+--+--+--+
| 1| 2| 3| 4| 5|
+--+--+--+--+--+
| 6| 7| 8| 9|10|
+--+--+--+--+--+
|11|12|13|14|15|
+--+--+--+--+--+
|16|17|18|19|20|
+--+--+--+--+--+
|21|22|23|24|25|
+--+--+--+--+--+
-----+--+--+--+--+
| 1| 2 3| 4 5||
+---+--+----+-----+
| 6 | 7 |8| 9 | 10 |
+ +--+ +----+----|
|11|12 13|14 15|
+---+---|----|----|--- +
|16 |1718|19|20|
+--+--+--+----+----+
|21| 22 |23 |24|25|
+--+--+--+-----+---+
1,6,7,11,16 (41)
2,3,8,12,13,17,18 (73)
19,21,22,23,24 (109)
9,14,15,20,25 (83)
4,5,10 (19)
Edited on July 21, 2023, 1:17 am
Puzzle Answer
