Arnav Sharma, from Reading town in southern England, passed the infamously difficult test a few weeks ago with zero preparation and had never seen what a typical paper looked like before taking it.
His mark in the exam, which primarily measures verbal reasoning ability, puts him in the top one per cent of the nation in terms of IQ level, The Independent reported.
"The Mensa test is quite hard and not many people pass it so do not expect to pass," Arnav said. "I took the exam at the Salvation centre and it took about two and a half hours," he recalled, adding there were about seven or eight people there. A couple of them were children but the rest were adults.
Arnav insisted he was not anxious before sitting for the test, saying "I had no preparation at all for the exam but I was not nervous. My family were surprised but they were also very happy when I told them about the result."
Meesha Dhamija Sharma, his mother, said she kept her "fingers crossed" for the whole exam. "I was thinking what is going to happen because you never know and he had never seen what a paper looks like," she explained.
"At one-and-a-half years old I took him to India for a holiday to see his grandparents, his grandmother told me about him and said Arnav is going to do very well with his studies," she said.
It was not until he was two-and-a-half years old that she became aware of his mathematical prowess. "He was counting up to more than 100. That was when I stopped teaching him because I came to know that there is no end to his numbers," she said.
Arnav, who attends Crossfields School on the outskirts of Reading, has been selected for Eton College and Westminster, both highly competitive and sought-after schools.
But it is worth noting his talents are not restricted to numbers. Arnav used to have a passion for singing and dancing and reached the semi-finals for 'Reading's Got Talent' for dancing with a bollywood act when he was eight.
"It is a high mark which only a small percentage of people in the country will achieve," a spokesperson for Mensa said.
Mensa is believed to be the largest and oldest high IQ society in the world. Membership is open to anyone who can demonstrate an IQ in the top 2 per cent of the population, measured by a recognised or approved IQ testing process.
It was founded in 1946 in Oxford by Lancelot Lionel Ware, a scientist and lawyer, and Roland Berrill, an Australian barrister, but the organisation later spread around the world.