def integer_to_base(number, base_string):
    """
    Converts base10 integer to baseX integer (where X is the length of base_string, say X for '0123' is 4),
    for example: 2645608968347327576478451524936 (Which is 'Hello, world!') to 21646C726F77202C6F6C6C6548 (base16),
    does not account for negative numbers
    """

    digits = []
    base_length = len(base_string)

    while number:
        digits.append(base_string[number % base_length])
        number //= base_length

    return ''.join(list(reversed(digits)))