# The Intriguing Nature of the Interesting Number Paradox

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## Chapter 1: The Fascination with Favorite Numbers

What’s your favorite number? This question often sparks intriguing conversations among friends and acquaintances. Personally, my favorite number is 5. When asked why I favor this number, my reasoning might come off as whimsical (pun intended).

The way the number 5 divides into tens captivates me. It’s also amusing that I have five fingers on each hand and five toes on each foot. Additionally, the number 5 possesses an appealing curve alongside its straight edges, and let’s not forget, it’s a prime number!

I’m certain you have your own quirky rationale for your preferred number. Is it a single-digit digit, or perhaps a double-digit one? I even ponder whether someone out there favors the number 26879542. So many inquiries arise, yet they often lead to equally whimsical answers.

### Section 1.1: The Intriguing Question of "Interesting" Numbers

This brings us to a thought-provoking inquiry: Can we categorize every natural number (1, 2, 3…) as either “interesting” or “uninteresting”?

Attempting to do so leads us to a comical paradox known as the Interesting Number Paradox.

#### Subsection 1.1.1: Understanding the Interesting Number Paradox

Before delving into the paradox, let’s recall a famous anecdote from the realm of mathematics. During a conversation, G.H. Hardy mentioned that the number 1729, which appeared on the taxi he had just taken, seemed rather dull.

In response, Ramanujan argued that 1729 is fascinating because it is the smallest number expressible as the sum of two cubes in two different ways. While this exchange was lighthearted banter between two esteemed mathematicians, it serves as an excellent segue into our topic.

In 1945, Edwin F. Beckenbach wrote a short letter in The American Mathematical Monthly, humorously suggesting that every natural number is interesting, and none are uninteresting. He whimsically demonstrated this through induction and contradiction.

- The number 1 is a factor of all positive integers.
- The number 2 is the smallest prime.
- The number 3 is the smallest odd prime.
- The number 4 is Bieberbach’s number.

...

Now, let’s assume there exists a non-empty set of uninteresting natural numbers. By definition, this set must contain a smallest number, which we’ll call ‘i’. However, since ‘i’ is the smallest uninteresting number, it paradoxically becomes interesting!

Thus, ‘i’ is removed from the uninteresting set and added to the interesting one. This process continues, with a new number ‘j’ taking the place of the smallest uninteresting number, which also becomes interesting, creating a cycle. Eventually, this leads to the conclusion that the set of uninteresting numbers becomes empty.

And that succinctly illustrates the Interesting Number Paradox — trying to define uninteresting numbers leads to contradiction.

### Section 1.2: Historical Context and Discussion

When Beckenbach shared his original “proof” in 1945, it was likely intended to be humorous. He concluded with the playful question: “Is this proof valid?”

Mathematicians discussing the Interesting Number Paradox often do so in jest, reveling in its subjective nature. Martin Gardner later characterized this paradox as a “fallacy” in his 1958 Scientific American column. David Wells notably identified the number 39 as the first uninteresting number, which only serves to make it more interesting — another contradiction!

## Chapter 2: Personal Reflections on the Paradox

In my view, the Interesting Number Paradox showcases the humor shared among mathematicians. Logically, it’s difficult to impose a binary classification on potentially infinite subjective outcomes, which circles back to my initial point.

Why do I prefer the number 5? Simply because I like it more than any other number! Any explanation I provide is likely to be subjective and may seem irrational to someone with different preferences.

Where do you fit into this discussion? Do you have multiple favorite numbers?

The first video explores the nature of the Interesting Number Paradox, discussing its background and implications in mathematics.

The second video delves deeper into the concept of interesting numbers, offering viewers a comprehensive understanding of the paradox.