list1=['400160', '400161', '400162', '400163', '400164', '400165', '400166', '400167', '400168', '400169', '400170', '400171', '400172', '400173', '400174', '400175', '400176', '400177','99990', '99991', '99992', '99993', '99994', '99995', '99996', '99997', '99998', '99999']
list1.sort()

#printing the last element
print("Largest element is:", list1[-1])
#print max(list1)

print("Largest element is:", list1[-1])
('Largest element is:', '99999')

In [40]: list1=['400160', '400161', '400162', '400163', '400164', '400165', '400166', '400167', '400168', '400169', '400170', '400171', '400172', '400173', '400174', '400175', '400
    ...: 176', '400177','99990', '99991', '99992', '99993', '99994', '99995', '99996', '99997', '99998', '99999']

In [41]: list1 = list(map(int,list1))

In [43]: max(list1)
Out[43]: 400177

max(list1, key=int)
# '400177'

max(map(int, list1))

400177

list1=['400160', '400161', '400162', '400163', '400164', '400165', '400166', '400167', '400168', '400169', '400170', '400171', '400172', '400173', '400174', '400175', '400176', '400177','99990', '99991', '99992', '99993', '99994', '99995', '99996', '99997', '99998', '99999']
print(max(map(int, list1)))

>>>python3 test.py
400177

max(map(int, list1))