RSA: If n=35, show that e will equal d
The number 24 has the curious property that, for any prime $p &gt; 3$, $p^2 - 1$ is divisible by 24.  (In fact, this holds for any odd number $p$ not divisible by 3.)

This follows simply from the fact that $p^2 - 1 = (p-1)(p+1)$; since $p$ is not divisible by either 2 or 3,


the factors $p-1$ and $p+1$ must both be even,
one of them must be divisible by 4, and
one of them must be divisible by 3.


Thus, their product must be divisible by $2\cdot4\cdot3 = 24$.