The nextprime function returns the smallest prime that is larger than n. The prevprime function returns the largest prime that is less than n.

$\mathrm{nextprime}\left(1\right)$

$2$

$\mathrm{nextprime}\left(0\right)$

$2$

$\mathrm{prevprime}\left(2\right)$

Error, (in prevprime) there are no primes less than 2

$\mathrm{nextprime}\left(25\right)$

$29$

$\mathrm{prevprime}\left(3\right)$

$2$

$\mathrm{prevprime}\left(25\right)$

$23$

$\mathrm{nextprime}\left(31243\right)$

$31247$

$\mathrm{prevprime}\left(2338714\right)$

$2338703$

$\mathrm{nextprime}\left(2^6\right)$

$67$