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## 'Special 24' printed from http://nrich.maths.org/

The number $24$ is special because it is just one short of being a square number.

So $24 + 1 = 25$ and $5^2 = 25$

AND when you double $24$ the answer is also one short of being a square

number.

So $24 \times 2 = 48$ and $48 + 1 = 49$ and $7^2 = 49$.

Find another number that is special in the same way as $24$.