What is your Erdős number? Mathematicians, although positive people, have their own "obsessions." One of these is the famous Erdős number, which "scores" their colleagues based on their relationship with the great Hungarian mathematician (due to Erdős's numerous collaborations with other mathematicians). Paul Erdős – and only he – has the number 0. Everyone else is scored based on their relationship with him. Anyone who has co-authored a paper with Erdős is scored 1, anyone who has co-authored a paper with someone who co-authored with Erdős is scored 2, and so on.

Addicted to coffee and amphetamines, hyperactive, with crystal-clear thinking, brilliant and humorous, he was eager to generously share his groundbreaking ideas with anyone willing to give him a little space and eager to intrigue their minds. An intellectual journey into Erdős's mathematical universe was not only a full enjoyment activity but also a first-class update on new theorems and proofs for everyone.

The man who believed that "ownership is a great hassle" had no permanent residence, nor a car. He needed no checks to write, nor income taxes to pay. The eccentric Paul Erdős was a nomad in the land of mathematics. He traveled from place to place, knocked on the doors of his colleagues, and declaring "my mind is open," announced to the respective "host" a new mathematical problem (for solution) or his groundbreaking proof of an unsolved conjecture.

His legendary memory and knowledge in various mathematical fields made Paul an inexhaustible source of specialized information. "In the years before the internet, there was Erdős," said those friends who generously cared for the maintenance of this unforgettable, lovable mathematical figure who discovered – like hidden treasures – universal ideas and equated brilliant proofs with poetry.

Paul Erdős, one of the most important mathematicians of the 20th century, and undoubtedly the most eccentric, had already been recognized internationally as a child prodigy by the age of seventeen. The meaning of his life was the formulation of mathematical conjectures and the solving of mathematical problems. Thanks to his astonishing work in Combinatorics, Graph Theory, Number Theory, Probability Theory, and Set Theory, he earned the title of the most prolific mathematician who ever lived.

Bruce Schechter holds a PhD in physics from MIT. He has worked as a content editor at Physics Today and as an editor at Discover. The book My Mind is Open, witty and full of mathematical puzzles that fascinated Erdős – and continue to thrill mathematicians today – tells the story of this strange genius. Bruce Schechter lifts the veil on the most surreal closed club and reveals the strange life of the world's most productive mathematician. Page by page, we become so connected with this charismatic gentleman that, by the end of the book, we feel unfortunate that we never met him.