HP 39gs Master Manual page 351

We can now test to see if this is a prime number by using the
function from the
MATH
CAS function list as shown right.
It returns a value of (false) indicating that it is not a prime number.
0
Using the function from the
FACTOR
are 641 and 6700417.
Note: The
ISPRIME?
14
10 . Beyond that level the results are highly probable to be
correct but not guaranteed. They are obtained using "Rabin's
Algorithm" and are called 'pseudo primes'.
menu. This is found in the Integer section of the
menu shows that its factors
function gives correct results for integers up to
ISPRIME?
351