"Suppose aliens invade the earth and threaten to obliterate it in a year's time unless human beings can find the Ramsey number for red five and blue five. We could marshal the world's best minds and fastest computers, and within a year we could probably calculate the value. If the aliens demanded the Ramsey number for red six and blue six, however, we would have no choice but to launch a preemptive attack."

"Television is something the Russians invented to destroy American education."

"The SF created us to enjoy our suffering. … The sooner we die, the sooner we defy His plans."

"Some French socialist said that private property was theft … I say that private property is a nuisance."

"My brain is open!"

"If numbers aren't beautiful, I don't know what is."

"It is not enough to be in the right place at the right time. You should also have an open mind at the right time."

"Végre nem butulok tovább"

"We'll continue tomorrow — if I live."

"This one's from the Book!"

"SF means Supreme Fascist — this would show that God is bad. I don't claim that this is correct, or that God exists, but it is just sort of half a joke. … As a joke I said, "What is the purpose of Life?" "Proof and conjecture, and keep the SF's score low." Now, the game with the SF is defined as follows: If you do something bad the SF gets at least two points. If you don't do something good which you could have done, the SF gets at least one point. And if nothing — if you are okay, then no one gets any point. And the aim is to keep the SF's score low."

"God may not play dice with the universe, but something strange is going on with the prime numbers."

"A mathematician is a machine for turning coffee into theorems."

"The first sign of senility is that a man forgets his theorems, the second sign is that he forgets to zip up, the third sign is that he forgets to zip down."

"Let n be an integer."

"Erdős knows about more problems than anybody else, and he not only knows about various problems and conjectures, but he also knows the tastes of various mathematicians. So if I get a letter from him giving me three of his conjectures and two of his problems, then it's sure that these are exactly the kind of conjectures and problems I'm interested in, and these are exactly the kind of questions I may be able to answer. Of course, this applies not only to me, but to everybody else. So Erdős has an amazing ability to match problems with people. Which is why so many mathematicians benefit from his presence. Every letter is likely to inspire you to do some work, or every phone call will give you some problems you are interested in."

"Paul Erdős is the consummate problem solver: his hallmark is the succinct and clever argument, often leading to a solution from "the book". He loves areas of mathematics which do not require an excessive amount of technical knowledge but give scope for ingenuity and surprise. The mathematics of Paul Erdős is the mathematics of beauty and insight."

"One of my greatest regrets is that I didn't know him when he was a million times faster than most people. When I knew him he was only hundreds of times faster."