sub proper-divisors (int $number --> int)
{
    my int $candidate = 0;
    my int $divisors = 1;
    # my int $number_sqrt = $number.sqrt.Int + 1;
    for 2 .. $number.sqrt.Int + 1 -> $candidate
    {
        $divisors = $divisors + 2 if $number %% $candidate;
    }
    $divisors + 1;
}

sub find-number(--> int) {
    my int $record = 0;
    my int $triangle = 21;
    for 7..Inf {
        $triangle = $triangle + $_;
        my $result = proper-divisors($triangle);
        if $result > $record {
            $record = $result;
            say $record, "-", $_;
        }
        if $result > 500 {
            return $triangle;
        }
    }
}

say find-number();