Calculate the two closest factors of an integer in Python

closest_factors.py

def calc_closest_factors(c: int):
    """Calculate the closest two factors of c.
    
    Returns:
      [int, int]: The two factors of c that are closest; in other words, the
        closest two integers for which a*b=c. If c is a perfect square, the
        result will be [sqrt(c), sqrt(c)]; if c is a prime number, the result
        will be [1, c]. The first number will always be the smallest, if they
        are not equal.

    """    
    if c//1 != c:
        raise TypeError("c must be an integer.")

    a, b, i = 1, c, 0
    while a < b:
        i += 1
        if c % i == 0:
            a = i
            b = c//a
    
    return [b, a]