Semiprime numbers are natural numbers that are products of exactly two (possibly equal) prime numbers.


Semiprimes   are also known as:

   semi-primes
   biprimes
   bi-primes
    2-almost    primes
   or simply:    P2  


Example
 
   1679  =  23 × 73  

(This particular number was chosen as the length of the Arecibo message).



Task

Write a function determining whether a given number is semiprime.



See also

 The Wikipedia article:  semiprime.
 The Wikipedia article:  almost prime.
 The OEIS sequence:  A001358: semiprimes  which has a shorter definition: the product of two primes.


sub is-semiprime (Int $n --> Bool) {
    not $n.is-prime and
        .is-prime given 
        $n div first $n %% *, flat grep &is-prime, 2 .. *;
}
 
use Test;
my @primes = flat grep &is-prime, 2 .. 100;
for ^5 {
    nok is-semiprime([*] my @f1 = @primes.roll(1)), ~@f1;
    ok  is-semiprime([*] my @f2 = @primes.roll(2)), ~@f2;
    nok is-semiprime([*] my @f3 = @primes.roll(3)), ~@f3;
    nok is-semiprime([*] my @f4 = @primes.roll(4)), ~@f4;
}