Shakuntala Devi was a very great Indian and had a strong capable mental calculator fit in her brain. She was famously known as Human Calculator or Human Computer. She mwas able to make ha place for heself in the 1982 edition of The Guinness Book of World Records.
Many of us can't even think of doing it. While, she correctly answered product of 13 digit numbers: 7,686,369,774,870 × 2,465,099,745,779 in 28 seconds, which can't be produced by our normal calculators too.