def is_pandigital(nb):
    """
    This function returns whether or not a number is 
    a 1-9 pandigital number, i-e it can be writted with 
    integers from 1 to 9.
    """
    if len(str(nb)) == 9:
        for i in range(1, 10):
            if str(i) not in str(nb):
                return False
        return True
    else:
        return False