Are you serious...
Python, is, naturally supporting long integer, which should be the very first concept to learn in any toturials...
witch means

Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 27 2018, 04:59:51) [MSC v.1914 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> 7777777777777777777777777
7777777777777777777777777
>>> 42949672960
42949672960

Oh, i guess i know what confuse you

>>> 7777777777777777777777777/7
1.1111111111111111e+24
>>> 7777777777777777777777777//7
1111111111111111111111111

Created this kata just keeping time complexity in mind.
How can we declare long integers in python 3, could you please help me here?

It may not be a direct duplicate to existed katas, but due to the well-known formula and the diffculty of this task, you are not adding new/interesting things to CW.
Please unpublish and solve more katas so that you can create something interesing new to CW.

Also, Needs Random Tests.

And, it's Python, with builtin BigNumber support
so what are you doing with 5.0000000005e+19?

Some words scores aren't right, both 'yyrxyvaci' and 'skowctpqmo' score is 152 so, following this:

If two words score the same, return the word that appears earliest in the original string.

the first one is 'skowctpqmo'

Approved