Funbers 16, 17 and 18

The fun facts about numbers that you didn’t realise you’ve secretly always wanted to know…

Oxford University
Jul 4 · 5 min read


Not only is sweet sixteen the title of one of the best/worst (delete as appropriate) television shows ever to exist (which is somehow still going — the trailer for the new season is below), it is regarded around the world as the first real step into adulthood. In the UK you can leave school and find a job, you can play the national lottery and you can also legally have some fun under the sheets…

Sixteen is also big in the world of sleep. Most humans will spend an average of 16 hours awake per day. I say humans, because in the animal kingdom it varies considerably. Your pet dog for example is awake for around 10 hours per day and your cat only 9 (classic cats). However, the laziest animal in the world is the Brown Bat, sleeping on average 20 hours per day. I’d like to think the other 4 are spent biting the necks of sleeping humans and practicing Transylvanian accents.

One of the most interesting facts about the number 16 is that it is used for the RGB colour coding system in web design. Have you ever played around in Photoshop (or the more budget Paint) and tried to select a custom colour? You’re faced with three numbers for Red, Blue and Green, that range from 0 to 255. In web design these numbers are converted into base 16, where 0–9 appear as numbers and then 10–15 are assigned the letters a-f. Consider the colour purple for example, its RGB value is (128, 0, 128). Converting that into base 16 you have (8 x 16) + (0 x 1) = 128, (0 x 16) + (0 x 1) = 0, (8 x 16) + (0 x 1) = 128 and so the final value is 800080. The two numbers/letters represent how many lots of 16 = 1⁶¹ and how many lots of 1 = 160 you need to make the colour value between 0 and 255. There’s a few more examples below for good measure.


Pick a number between 1 and 20… how many of you said 17? Seventeen is called a ‘psychologically random number’ because it comes up more often than it should when people are picking random numbers. The even numbers have a nice pattern, as do numbers ending in 0 or 5, which just leaves those ending in 1, 3, 7 or 9. A lot of these numbers also tend to be prime numbers (only divisible by 1 and itself) which makes them even more appealing. 17 fits both rules which is why it’s so popular.

Now remember when I said thirteen was the unluckiest number in the world? (If you don’t you should go back and read the previous funbers article — it’s great) Well, seventeen wants a word. In Italy, the number 17 is feared because in Roman numerals it reads XVII, which can be rearranged to spell Vixi meaning ‘I am dead’. It may sound a little far-fetched, but Renault was so worried by the superstition that it changed the name of its R17 model to R117 for the Italian market. Looking at the R17 below I’d say shoddy engineering is more likely to be the cause of death rather than the number 17… how small are those wheels?!


Eighteen is another big number for symbolising adulthood in many cultures, perhaps none more so than in democratic countries where in most cases it is the age at which you are eligible to vote. This hasn’t always been the case, however, as during the Vietnam War the voting age in the US was 21, which meant that you could be conscripted into the army to defend the democratic freedom of the people of Vietnam, but yet not be able to vote yourself back at home. Fortunately this did lead to the age being lowered to 18 in 1971.

In the UK, most people celebrate their eighteenth by having an alcoholic drink or two… or more accurately getting drunk/smashed/wasted/bungalowed/any other word used to describe being intoxicated. The reason being that eighteen is of course the legal age of drinking in the UK and is the most popular choice around the world, with a few notable exceptions… To drink in Egypt or the US you must be 21 and it’s completely illegal in some countries such as Libya, Saudi Arabia and Iran. Other countries are a little more ‘lax’ with their laws, — I’m looking at you Haiti — as they have no restriction on the age at which you can consume alcohol, although apparently in Haiti it is often restricted to those of at least ‘school age’, which is the ripe old age of 6…


The Funbers series is written and presented by Dr Tom Crawford and is broadcast weekly on BBC radio. For more maths fun check out Tom’s website and follow him on Twitter, Facebook, Instagram and YouTube @tomrocksmaths.

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Want to read more? Try our articles on Funbers 13, 14 and 15, Funbers 10, 11 and 12, and Funbers 7, 8 and 9.

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Oxford is one of the oldest universities in the world. We aim to lead the world in research and education. Contact:

Oxford University

Oxford is one of the oldest universities in the world. We aim to lead the world in research and education. Contact:

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