Think of a number. Whichever. **It doesn't matter if it is a one-digit or hundreds-digit number**. Any number you think probably has an interesting story behind. For example, without going far, the number zero: entire books have been written about it: it first appeared in Babylon in the third century BC. C.

**And the 1?** It was the first issue in history. Mathematically it is unique for many reasons: when multiplying it by any other number, it does not vary. **If it is divided by itself, 1 remains**. The 1 is both the first and second terms of the Fibonacci sequence. The next term in the sequence is 2. In many cultures, 1 is represented by a dot or a stroke (horizontal, vertical or more or less sinuous).

**And the 2?** It is a symmetric number in the animal kingdom. Two arms, two eyes, two legs. It is the value of the constant n of Fermat's theorem. It is the first prime number. It is the only even prime number, since the other pairs are multiples of 2 (they are not prime). It is the atomic number of helium.

And so we could continue *ad infinitum*. The other day, for example, I was talking about **the significance of number 23**. No wonder, then, that all two-digit numbers, and many of three, **have even your own article on Wikipedia**.

**And the 77?** It is the sum of the first eight prime numbers: 77 = 2 + 3 + 5 + 7 + 11 + 13 + 17 + 19. It is the atomic number of the iridium (Go). There is a network of artificial communications satellites called Iridium because initially it was thought that there would be 77 satellites.

And also larger numbers. Wikipedia also dedicates an article to the number 9.814.072.356: **it is the largest holodigital square that exists**, that is, the largest squared number that contains all decimal digits exactly once.

Thus, between prime numbers, perfect, square, cubes and so on, it is frankly difficult to find a number that was not interesting. In fact, if we find it, why would it be uninteresting? In the opinion of **James Gleick**in his book *Information*:

Surely there will be a number on which there will be nothing special to say. Wherever you are, it is a paradox: the number that we could describe in a very interesting way as "the smallest interest-free number".

And the 1729? For **G. H. Hardy**, who took taxi number 1729 when in 1917 he went to visit **Srinivasa Ramanujan**, commented that this number seemed quite bland. Ramajunan did not agree: that number was the smallest that can be expressed as the sum of two cubes in two different ways. This anecdote also gave luster to the number, which is also the number of Carmichael, a pseudo-cousin of Euler, and a number of Zeisel.