def num_add_commas(num):
    """
    Adds commas to a numeric string for readability.

    Parameters
    ----------
        num : int
            An int to have commas added to.

    Retruns
    -------
        str_with_commas : str
            The original number with commas to make it more readable.
    """
    num_str = str(num)

    str_list = list(num_str)
    str_list = str_list[::-1]

    str_list_with_commas = [
        f"{s}," if i % 3 == 0 and i != 0 else s for i, s in enumerate(str_list)
    ]

    str_list_with_commas = str_list_with_commas[::-1]

    return "".join(str_list_with_commas)