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Number 20: Happy silly season

Kids putting their maths skills to the test by counting how many more sleeps til Santa comes. Watch me in conversation with futurist Amy Webb at SXSW. And was Plato ever wrong?

It’s well and truly the silly season, and so much fun watching my little nieces and nephews putting their maths skills to the test by counting down how many more sleeps til Santa comes. I couldn’t find much 20 trivia related to Christmas, but here goes…

  • Every year a giant Christmas tree is installed in NYC's Rockefeller Center. This annual tradition began in 1931 when workers pooled their money to buy a 20 feet (6 metres) balsam fir decorated with garlands handmade by their families. This year’s tree towers 80 feet (24 metres) and is adorned with 50,000 energy-efficient LEDs, yet it still falls significantly short of the record 100 feet tree that wowed New Yorkers in 1999!

  • Pop culture credits Coca-Cola with inventing the modern Santa Claus wearing his red and white suit vis-a-vis this global behemoth's 1920s advertising campaigns. Whilst that’s not true, Coca-Cola’s ads certainly helped to commercialise the spirit of Christmas, which is today celebrated by billions of people worldwide including many like myself for whom the day is moreso cultural than religious.

Now, let’s jump into something a bit more mathematical shall we!

God’s number

One of the biggest selling and coolest toys of all time would have to be the Rubik’s Cube. Six faces, 6 colours, and over 43 million, million, million possible arrangements – all of which can be solved!

So if you drew a picture of every possible arrangement and beside each wrote the number of moves it takes to solve that cube, you’d be able to look at that list of numbers and calculate ‘the most moves required to solve any possible arrangement of a Rubik’s Cube’.

Obviously drawing up the list would be a problem. If you could draw a diagram for a cube and write down the move number in just one second the list would take 81,000,000,000,000,000,000 years – which could slow down the whole process a bit.

Regardless, this number is called ‘God number’ by many mathematicians – the joke being that if God exists, he or she could certainly solve any Rubik’s Cube in as few moves as possible.

In 2010, American cuber Tomas Rokicki and his pals proved that any Rubik’s Cube can be solved in at most 20 moves. They reduced the 43,252,003,274,489,856,000 possible arrangements of a cube into 55,882,296 ‘typical’ cases and solved each of them. This took effectively 35 CPU-years of idle computer time donated by the nice people at Google Labs.

This was time well spent if you ask me. And since then the number 20 amongst Rubik’s enthusiasts is known as ‘God’s number’!

Could you win a face-off with an icosahedron?

A regular icosahedron has 20 faces - all of them equilateral triangles which is another way of saying triangles with all 3 sides of equal length. This shape is one of the 5 Platonic solids known to the Greek philosopher Plato as far back as 350 BC when he mentioned them in a handy little page-turner called Timaeus that he banged out around this time.

Although he possessed an extraordinary grasp of geometry for his era, Plato also thought that the icosahedron was the shape of the smallest occurring particles of water, which he considered one of the fundamental elements or building blocks of everything in the universe.

However, Plato was proven to be, how shall we say, ‘not quite so correct’, but hey, that’s easy for us to say in the modern world with our swag electron microscopes and the like.

Having 20 faces gives the icosahedron the most faces of any of the Platonic solids.

Fascinating fast facts about 20!

Seizing Caeser

In 75BC, Julius Caeser was kidnapped by pirates. Unaware of his superstar celebrity status, the pirates demanded a measly 20 talents in ransom. Caesar was held for 38 days before the ransom was paid, at which time he promptly raised a naval force, captured the pirates, and had them executed. Baller!


‘20/20 vision’ is normal vision, meaning you can see from 20 feet away what the average individual can see. Hawks and other birds of prey may have 20/2 vision – meaning they can spot, from 20 feet, what normal humans see at 2 feet. The best human vision is around 20/8.


The Ancient Mayans used 20 as the basis for their number system known as vigesimal (as opposed to our base 10 or decimal system). One of their many calendars featured 13 months of 20 days each. This 260-day cycle was known as a Tzolkin and contained days with really cool names like Chikchan, Kawak and Ok.

Rock and roll

I place two 20 cent coins next to each other so that they are touching and both with the number 20 displayed upwards (as pictured below).

If I keep coin B fixed in place and roll coin A around it, going underneath coin B, when it gets to the other side will the 20 be written up or down? And if I rolled A over the top of B would the answer be any different?

Have a think, then go get your wallet and give it go.

The edge of tomorrow: Watch this SXSW keynote by futurist Amy Webb, hosted by me!

I was thrilled to recently be in conversation with Futurist and CEO of the Future Today Institute, Amy Webb, at SXSW in Sydney.

Above you can watch a free recording of this keynote address, where Amy shares what's on the edge of tomorrow and gives a deep dive into the emerging tech trends that will shape the next decade.

SXSW Sydney was the first to hear about the innovations shifting paradigms, challenging conventions, and shaping the everything from business to government and everyday life.

A summer gift for you

Looking for some holiday reading? Get a 20% discount on any of my books purchased via using the code summer20. Valid til 31 December 2023 11.59pm

#19 winner

Thanks to those of you who correctly calculated that the 19th Fibonacci number is 4181 which is not prime - it is 37 x 113.

I randomly drew John Switala from the entries received and sent him a copy of my Big Book of Numbers for his grandkids Charlie, Kenzie, and Casie. Happy Christmas kids!

That’s all from me for 2023. Happy holidays and I will be back with number in the new year.. If you'd like more geeky fun, please check out my other newsletters below.

Yours in numbers,



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