def odd_digits(num: int) -> bool:
    """
    Check if the number passed as argument has only odd digits.
    >>> odd_digits(123)
    False
    >>> odd_digits(135797531)
    True
    """
    num_str = str(num)
    for i in ["0", "2", "4", "6", "8"]:
        if i in num_str:
            return False
    return True