def try_parse_int64(string):
    """Converts the string representation of a number to its 64-bit
    signed integer equivalent.

    Parameters
    ----------
    string : str
        string representation of a number

    Returns
    -------
    int or None
        The 64-bit signed integer equivalent, or None if conversion
        failed or if the number is less than the min value or greater
        than the max value of a 64-bit signed integer.
    """
    try:
        ret = int(string)
    except ValueError:
        return None
    return None if ret < -2 ** 64 or ret >= 2 ** 64 else ret
