What do Spinal Tap, Stranger Things and the Australian Cricket team have in common? That’s right, the first two-digit prime number – 11!

## Let's start with some pop culture

Readers of my vintage might pin their pop-culture 11 badge to the movie Spinal Tap about an English Rock Band who play so loud they have an amplifier that goes beyond what any other amp can do. It leads to this seminal and hilarious exchange with a bemused rock journalist

Marty:

Nigel: It's very...very special because if you can see... Marty: Yeah... Nigel: ...the numbers all go to eleven. Look...right across the board. Marty: Ahh...oh, I see.... Nigel: Eleven...eleven...eleven.... Marty: ...and most of these amps go up to ten.... Nigel: Exactly. Marty: Does that mean it's … louder? Is it any louder? Nigel: Well, it's one louder, isn't it? It's not ten. You see, most...most blokes, you know, will be playing at ten. You're on ten here...all the way up...all the way up.... Marty: Yeah.... Nigel: ...all the way up. You're on ten on your guitar...where can you go from there? Where? Marty: I don't know.... Nigel: Nowhere. Exactly. What we do is if we need that extra...push over the cliff...you know what we do? Marty: Put it up to eleven. Nigel: Eleven. Exactly. One louder. Marty: Why don't you just make ten louder and make ten be the top…number...and make that a little louder? Nigel: (after a gorgeous pause)...these go to eleven.

Even astrophysicists aren’t immune. In 2015 when they discovered the brightest supernova-like object ever observed (the creatively named ASASSN-15lh clocking in at 570 BILLION times brighter than our sun), Krzysztof Stanek, a professor of astronomy at Ohio State University channeled Nigel Tufnel when he remarked, “It’s as if nature took everything we know about magnetars and turned it up to 11!”

## 11x multiplication pyramid

#### In around year 3 you learned that 11 x 11 = 121. And by the end of primary school, most kids should be able to work out (okay dad, grab the calculator) that 111 x 111 = 12321.

Well bang out 1111 x 1111 and see that it equals 1234321. See a pattern in the triangle above? Yep, and it is gorgeous.

Over the years I’ve lost count of the number of people who have been blown away by the beauty of this.

## Enjoy these fascinating numerical facts about 11!

Spare me a Loonie

Spare me a Loonie Canada’s one-dollar coin has 11 sides (a hendecagon) and features the North American aquatic bird, the common loon, leading to the coin being known as a “loonie”. Also on the topic of 11, Canada’s flag features a maple leaf with 11 points!

11/11 singles shopping bonanza With sales exceeding $200 billion in 2021, China’s 24-hour Singles Day shopping festival is so named because the date represents four singles standing together. Also known as Double 11, it was started by Nanjing University students as a sort of anti-Valentine’s Day for lonely singles wanting to spoil themselves.

Stranger Thing’s Eleven Fans of this Netflix mega-sensation know Eleven’s rare telekinetic ability allows her to send bad guys to another dimension and contact unworldly creatures. El also falls in love with Mike, becomes a secret weapon against the evils of the Upside Down, and generally gets up to all sorts of scary fun.

Strobogrammatic prime number 11 is the smallest strobogrammatic prime number, which means it looks the same when it’s rotated 180 degrees, followed by 101, then 181. The most recent strobogrammatic year was 1961; we won’t have another one until 6009 – if the planet makes it that far.

## INSPIRATIONAL THINKERS & DOERS - Pat Cummins the cruciverbalist

At this year's earlier heavily rain-affected Sydney's Test Cricket, I was spruiking the McGrath Foundation during one of the many, yawning gaps in play. Who did I see over near the Aussie dressing room, but the fearless leader of our national 11, Pat Cummins?! Turns out he’s not just a lion-hearted fast bowler and an astute tactician – he also likes to wile away the hours waiting for a gap in the clouds with a bit of cryptic crossword action! For those who can remember the Aussie dressing room back when a rain break meant “break out a deck of cards and some ciggies”, this is quite a change indeed. It was a Friday – which as cruciverbalists (crossword fans) everywhere know – means the Sydney Morning Herald cryptic is the brutal brainchild of David Astle of ABC Radio Melbourne and SBS's Celebrity Letter and Numbers fame. It is as tough as they come. I had an absolute blast spending 15 minutes steering Captain Pat through some pretty tough verbal headwinds. Suffice to say, he did better with the pen in hand than I would have with a bat and the roles reversed!

## Trivia time - win a book

11 is the largest number that is not expressible as the sum of two composite numbers. A composite number is one that can be written as the multiplication of two numbers neither of which are 1. E.g. 9 = 3 x 3 is composite, as is 20 = 4 x 5. But prime numbers like 7 = 7 x 1 are not composite. So, 12 can be written as the sum of two composite numbers; 12 = 4 + 8, where 4 and 8 are both composite (4 = 2 x 2, 8 = 2 x 4). Similarly 13 = 4 + 9, 14 = 6 + 8, 15 = 6 + 9 and so on, all of these being the sum of two composite numbers. We can keep going on from 15 and every whole number can be written as the sum of two composites. For a chance to win one of my books, what is the greatest even number not representable as the sum of 2 odd composite numbers? Just crunch it out and send your answer to number@adamspencer.com.au by 5pm AEDT Friday 31 March 2023. Winners of number 010 trivia Thanks to everyone who correctly calculated that squaring each of the numbers 32,043 and 99,066 resulted in answers containing the digits 0-9! I've randomly drawn two winners - Michael Will (who even sent me his longhand working!) and Margaret McCahon - and I will be in touch soon to get a copy of my book over to you both. Yours in numbers, Adam

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