# Why do people have a favorite number

## And what's your favorite number?

Numbers are not just those abstract objects that mathematicians deal with objectively and precisely. Numbers also play an important role in the world of emotions and even mysticism. So many people are afraid of the number 13, for example, that some airlines refrain from showing seats in the 13th row. The numbering then jumps from twelve directly to 14. In Brazil and Italy, on the other hand, 17 is considered an unlucky number. There is therefore no row 17 in Alitalia jets. These examples already show that numbers have a psychological effect that actually has an impact on everyday life.

While in Western countries the number four is considered a good luck charm - for example in the shape of a four-leaf clover - it is a harbinger of bad luck in China. In return, the eight promises great luck in the Far East. This is the reason why the phone numbers of restaurants, hotels or other companies in China usually contain many eights. And in Russia it is very important that you only give away an odd number of flowers in any case. An even number of flowers is perceived as an insult.

Many people have a favorite number. This also shows a special relationship between people and numbers. In the beginning there was the word, it says in the Bible. But although language is so immensely important to people, hardly anyone has a favorite letter - but a favorite number, just as one has a favorite color.

Federal Research Minister Annette Schavan, for example, who declared 2008 the year of mathematics, reveals that her favorite number is seven. The theologian has a comprehensible reason for this: "Because there are seven sacraments." The Berlin mathematician Martin Grötschel, who was honored with the Governing Mayor's Berlin Science Prize this year, calls seven his favorite number. But the professor at the Technical University has a completely different explanation: "Because seven is the largest single-digit prime number."

Mathematicians often seem to have a preference for certain numbers associated with a particular degree of abstraction. This is also suggested by the favorite number of Professor Günter M. Ziegler from Matheon in Berlin. Ziegler was the chief organizer of the "Year of Mathematics" and was awarded the Communicator Prize of the Stifterverband and the German Research Foundation for his commitment to science communication. Ziegler's favorite number is "42", the very number 42 that plays a central role in the novel and film "The Hitchhiker's Guide to the Galaxy". There it is the answer given by a huge supercomputer to the question of life, the universe and simply everything. "Then for several volumes it is about the name of the question to which answer 42 was given," says Ziegler, "that is a wonderful parody of the misconception that you can pack everything into a single question and everything with one answer a single number or with a single formula. Of course that is not possible. "

With brain researchers, the sympathy for numbers can turn out to be so differentiated that they differentiate between cardinal numbers - 1, 2, 3 - and ordinal numbers - the first, the second, the third. The favorite number of the Munich brain researcher Ernst Pöppel is "the third". His reasoning: "I believe that ordinal numbers are earlier than cardinal numbers in our thinking apparatus and that we were only able to develop the abstract concept of cardinal numbers, i.e. 1, 2 or 3, through ordinal numbers, i.e. 1, 2 or 3. But why the third? If there are only two things that are in a quantitative relationship to one another, I only need the concept of "more or less", so no concept of numbers that indicate an order relation. I can only get an order then speak when there is or could be at least the third that grants a 1st and 2nd the rank of an ordinal number. Thus the third is the origin of numbers in general. "

The famous British mathematician Sir Michael Francis Atiyah, who has been awarded both the Fields Medal and the Abel Prize for his work, is particularly drawn to the imaginary number "i", which is synonymous with the root of -1. “The number i is extremely useful in mathematics. And yet you can't really understand it. Gauss introduced this number because he believed it was needed. So this number was not discovered. It's a good example of that Numbers can be invented. "

If someone answers the question of their favorite number with the fraction 1/137, then you can be pretty sure that they are a physicist. The natural constants occurring in the theories of physics are normally numbers with an arbitrary sequence of decimal places. These numbers cannot be represented as a fraction. But there is one exception: the so-called fine structure constant, which plays an important role in atomic physics. It can be approximated fairly precisely by the fraction 1/137, with 137 also having the charm of being a prime number. For example, 1/137 is the favorite number of the physicist and German science astronaut Ulrich Walter.

But even the apparently simplest of all numbers, zero, is particularly valued by some. Zero is the favorite number of the biologist and President of the Max Planck Society Peter Gruss. Zero is easily underestimated, he explains. But without the zero there would be no decimal system and thus the basis for all modern mathematics would be missing. "Ultimately, the existence of this number is essential for all of the natural sciences," says Professor Gruss, and the binary system with which all computers work would be deprived of its basis without the zero.

The number 256 somehow "smells" of computing because it can be represented as the power of the number two. 256 is the favorite number of mathematician Jochen Brüning from Berlin's Humboldt University. However, he has no reason for this: "Actually, the number 256 is actually pretty boring. But somehow it stuck in my mind since I was a child, so that I can't give any account of its origin. Some things are just a matter of chance and not a deliberation. "

The favorite number of Matthias Kleiner, President of the German Research Foundation, sounds very much thought-provoking: It is 11320. How do you come up with such a favorite number? "This is made up of the birthdays of my three children who were born on the 11th, 3rd and 20th." Why not.

The famous circle number Pi (3.1415 ...) has a lot of friends, who sometimes even organize themselves in fan clubs and celebrate the "World Pi" on March 14th - because of the American date 3/14. The mathematician Ehrhard Behrends from the Free University of Berlin doesn't go that far, but Pi is clearly his favorite number, about which he also likes to give a public lecture. For the year of mathematics, Behrends played a key role in organizing the "Mathema" exhibition in the Berlin Technology Museum.

The year of mathematics is coming to an end these days. More than 500 partners from science, culture and politics have organized around 760 events in this context - regional and national, exhibitions, competitions, lectures, festivals, events and even a "math ship" that docked in 31 cities and more than 400 000 visitors. "The year of mathematics was a complete success," sums up Annette Schavan. So maybe more people will have a favorite number in the future.

PS: The author's favorite number is pi.