My favourite number is 137. It’s an odd choice: when surveyed, the vast majority of those who have a favourite number say theirs is under twenty, let alone a hundred.¹ But i have my reasons, starting with the fact that each digit alone is fascinating in its own right.

One needs no introduction, and can barely even be called a number in the traditional sense. It is both the building block from which every other number is built and the unmoving rock, the sole multiplicand that leaves any factor it touches unchanged. It is so fundamental that we barely think of it: if there is an apple in front of us on the table, we call it an apple, only invoking the numeral one if we might have been expecting two. More than that, it is τὸ Ἑν, the Monad, that from which all else flows forth; so sublime it is barely a thing, just as it is barely a number.

Three, on the other hand, is the magic number², and it has a way of getting in our heads. The technical term is hendiatris — things just sound better in threes. Think véní, vídí, vící; wine, women, and song; or liberté, égalité, fraternité. And how many cultures around the world have some sort of threefold God, be it the Holy Trinity, the Hindu Trimurti, or Julian’s “Zeus, Haides, and Helios in one”?

Seven is where things get interesting. For once i’ll dispense with the cultural and metaphysical aspects — it’s been done — and note a curious thing about our human number sense. If there are, say, four cows in a field, we can look and instinctually know that there are four cows, without needing to consciously count. Five and six are doable, but difficult, and vary based on age and person.³ But seven is where this sense breaks down. Beyond that barrier, we lose our intuitive animal sense, and we have to actually count. Seven is the number that sets us apart from the animals; if one and three are the numbers of the Gods, then seven belongs to humanity.

So, what do you get if you smush those three digits together? By some sheer coincidence, the most famous number in physics. The number 137 is, give or take a few hundredths⁴, the value of the fine-structure constant, one of the universe’s fundamental, unchanging values as etched into the standard model of particles. Nobody really knows why it has the value it has; as Richard Feynman once said, “It has been a mystery ever since it was discovered more than [a hundred] years ago, and all good theoretical physicists put this number up on their wall and worry about it.” (Worry they did: Wolfgang Pauli, the first man to theorise the neutrino, spent much time deliberating with Carl Jung on how this godforsaken 137 had wormed its way into the universe’s code, and why it might have done so.)

So, that’s why 137 is my favourite number. A remarkable figure, you might say.