If you are comparing greatest Mathematician Srinivasa Ramanujan and great Mental calculator Shakuntala Devi then it would be like comparing light intensity of Sun vs Moon.
so what’s the difference between two-
- Ramanujan derived many pre-discovered mathematical theorems on his own relating to himself with higher mathematics at the age of 13 while Shakuntala devi started solving many complex mathematical problems related to basic mathematics or arithmetic at the age of 5 . after it Shakuntala devi’s whole life she did astonishing fast calculations related to only this basic arithmetic. while Ramanujan had done basic mathematics almost same age as Devi.
- Ramanujan discovered many new mathematical theorems,functions and theories like analytical theory of numbers and worked on elliptic functions, continued fractions, and infinite series. some of them are much mysterious. one of them being used after 90 years of his death in Blackholes calculations in 2010 ! some of them are called mock theta functions and may be used in string theory too. do you find any such thing from Shakuntala devi? did Shakuntala Devi ever wrote any single research paper in mathematics other than solving old problems like finding 23rd root of 201 digit number and multiplying two 13-digit numbers 7,686,369,774,870 × 2,465,099,745,779 but doesn’t that an already solved problem ( means can be solved by anyone by taking much more time than devi who knows its algorithm).what ramanujan did seems almost impossible for worldwide mathies.
- Divine talent like Ramanujan is not find before him in whole human history of mathematics till now we are living in this year. while for Shakuntala devi there is alternative like American educator Scott Flansburg. Ramanujan was termed as exceptional ,unforgotten and greatest mathematicians by many persons like renown mathematician G.H. Hardy.
- Ramanujan died so early at the age of 32 while Shakuntala Devi died at the age of 83.
- Hollywood made biopic on Ramanujan while Bollywood made biopic on Shakuntala Devi.
Now you can see the difference in their life span and works and impression on human society in world.
from my attitude Shakuntala Devi was a great human calculator but not a mathematician at all although wikipedia includes her in that list. she was a good maths entertainer by solving already solved mathematical problems much faster than others but that is not quite a contribution to field of mathematics. Computers and Calculators of high accuracy and fastness can do what Shakuntala Devi did, but what Ramanujan did it’s very hard and till now is almost impossible for even Artificial intelligence and supercomputers.
so Srinivasa Ramanujan is one of the greatest mathematicians and incomparable to any human calculator or computer because his significant contribution to mathematics which is still yet to find its full use in future of physics thus in future technology and thus in human society.
P.S. - I respect Shakuntala Devi too because of her talent.Both these great people were born in poor family and both were Indian too. I love both.