Final answer:
The max() function is used to find the largest number in a list, which in the case of list [2445, 133, 12454, 123], would return 12454.
Step-by-step explanation:
If list1 is [2445, 133, 12454, 123], to determine the maximum value in this list, one would use the max() function in Python. This function iterates through the elements of the list and returns the largest one. Therefore, in executing max(list1), Python would compare the integers and return 12454, as it is the greatest number in list1.