sub get_nof2 {
    return scalar @{ divisors(+shift) };

}

{
my $D;
sub divisors {
    my $n = shift;
    foreach my $d ( 2 .. sqrt($n) ) {
        unless ( $n % $d ) {
            my $div = $n / $d;
            unless ( defined $D->{$div} ) {
              $D->{$div} = divisors($div); }
            return $D->{$n} =
              [ uniq( @{ $D->{$div} }, map { $d * $_ } @{ $D->{$div} } ) ];
        }
    }
    return $D->{$n} = [ 1, $n ];
}