top of page

Number 15: Old skool cool

Hanging with the stars, determining dermatoglyphics, necking a Melchizedek and books to be won. Thanks for reading my nerdy newsletter...

Throwback to the famous Fifteen Puzzle

The geek puzzle that defined the 1980s was the Rubik’s Cube. Well one hundred years earlier, this little mind bender was all the rage:

What is it, you ask? It’s Noyes Chapman’s famous ‘Fifteen Puzzle’ where you have to rearrange the squares by sliding them into the open space to eventually get them into numerical order from top left i.e. 1 – 2 – 3 ... 13 – 14 – 15.

If you take the tiles out and replace them randomly, the puzzle will only be solvable 50% of the time. For example, this one with 14 and 15 swapped is unsolvable.

The Fifteen Puzzle can be easily purchased today and even played online, so why not have a crack? Try beating chess supremo Bobby Fischer’s personal best at solving a Fifteen Puzzle in just 17 seconds.

Show-off! 😊

The hottest and coolest stars around

No, I'm not talking about this week's Logies! Stars were originally classified using a system of 15 letters ranging from A to O developed by Angelo Secchi in the 1860s. The letters A (hottest) to O (coolest) corresponded to the temperature of the stars.

This was replaced by the more sophisticated Morgan-Keenan (MK) system in the 1940s, which uses Roman numerals and considers additional factors such as the star’s luminosity and surface gravity.

Another person who knows a bit about classifying stars is astrophysicist extraordinaire Neil deGrasse Tyson who I was lucky enough to tour with in Australia this month. Thanks to the many subscribers to number who came to the shows and reached out on socials to say how much fun you had.

Of all the amazing subjects we traversed, the observation that most stayed with me is this:

Humans are often quoted as sharing almost 99% of our DNA with chimpanzees who cannot understand even the simplest of sentences we might utter, let alone our deepest insights into the universe. So, imagine if we ever encountered aliens with, say, another 1% different DNA to us. Apart from being advanced enough to make it to Earth, how much more intelligent than humans could they be?

Thought-provoking stuff indeed.

Fascinating facts about 15!

All the way with LJ

One of Australia’s greatest ever athletes, basketball champion Lauren Jackson wore the number 15 for Australia and the Seattle Storm in honour of her mother, Maree, who wore the same number at basketball world championships in the 1970s.

Those dermatoglyphics aren’t uncopyrightable!

Spelled using 15 different letters, ‘uncopyrightable’ is the equal longest word in English with no repeated letters. Its counterpart is the considerably more obscure ‘dermatoglyphics’, which is the study of fingerprints – and arguably copyrightable!

Did someone say pool party?

Because 15 is the fifth triangular number (1+2+3+4+5), it is the number of coloured balls in a standard game of pool. The most common form of pool is 8-ball, but variants include 9-ball, blackball, 10-ball, 7-ball, straight, bank, one-pocket and 61.

Basic maths

Everyone knows that 15 = 3 x 5 so you’d think that a computer proving that in 2001 would not be a big thing. But back then IBM factored 15 into 3 x 5 using a process called Shor’s algorithm. This was a landmark moment in deloping incredibly powerful quantum computers!

Could you neck a Melchizedek?

I know it’s Dry July but I also just really wanted to share this one…

While the standard wine bottle holds 750 millilitres, there are actually 15 different sizes available.

These range from the single-serve piccolo to the massive 30-litre Midas/Melchizedek, which is named after the Biblical King of Salem and would fill almost 250 champagne flutes.

Here’s a full list, though I can’t promise they’ll all be sold at your local bottle-o!

• Piccolo (0.25 bottle)

• Demi (0.5 bottle)

• Standard (1 bottle)

• Magnum (2 bottles)

• Jeroboam (4 bottles)

• Rehoboam (6 bottles)

• Methuselah (8 bottles)

• Salmanazar (12 bottles)

• Balthazar (16 bottles)

• Nebuchadnezzar (20 bottles)

• Melchior (24 bottles)

• Solomon (26.66 bottles)

• Sovereign (33.33 bottles)

• Primat or Goliath (36 bottles)

• Midas or Melchizedek (40 bottles)

Win a maths book!

Tooling around Twitter one day I discovered a cool observation by @jameselkins.

15 equals the sum of the consecutive integers between (and including) its first and second digits. I.e. 1+2+3+4+5=15

To win a copy of one of my books, tell me which other two-digit number has this same property. Email me the answer here by 30 July.

That's it for 15. If you'd like more nerdy fun, why not check out my other newsletters below?!

Yours in numbers,



Recent Posts

See All


Rated 0 out of 5 stars.
No ratings yet

Add a rating
bottom of page