from typing import List

def _prime_factors(x: int) -> List[int]:
    """
    Finds and returns the prime factors of a given integer.

    This function computes the prime factors of the input integer `x` and 
    returns them as a sorted list. It handles both even and odd numbers, 
    and includes any remaining prime number greater than 1 if applicable.

    Args:
        x (int): The integer to factorize. Must be a positive integer.

    Returns:
        list[int]: A sorted list of prime factors of the input integer.
    """
    # TODO: Implement this function
    pass