# How do you explain to &quot;slow person&quot; that 1 is not prime number?

• Any ideas? i already told him to look up Euclid on internet, but he's not willing to accept this "new idea".

• @Nagesh said:

Any ideas? i already told him to look up Euclid on internet, but he's not willing to accept this "new idea".
There is no explanation. It's simply a matter of definition. You can try explaining the consequences if 1 were prime, and hence the reason it's defined that way, but really it's just a matter of how the term 'prime' is defined - it excludes 1.

From Wiki: "A prime number (or a prime) is a natural number that has exactly two distinct natural number divisors: 1 and itself. " Obviously, therefore, 1, which only has one divisor, is not prime. The wiki page mentions some of the consequences of not defining it this way.

• If he's unwilling to even bother looking up something so simple, tell him he can believe whatever delusions he wants to, and the rest of the world will gladly live with being "wrong."

There's no reason his confusion should continue to be your problem, especially if he's fine with it.

• @intertravel said:

There is no explanation. It's simply a matter of definition. You can try explaining the consequences if 1 were prime, and hence the reason it's defined that way, but really it's just a matter of how the term 'prime' is defined - it excludes 1.

That doesn't solve anything, since the definition is pretty much tailor-made to excude 1 - it's easy to think up a different definition that contains all the intuitive properties of prime numbers but includes 1. (In fact, according to the wiki, 1 "was" a prime up until the 19th century, it only got changed when people began to find it ugly and cumbersome to write "all primes except 1" everywhere).

I think the suggestion of pointing out some consequences is a better one. I personally always found the example of prime factorization the most intuitive one - the whole idea that each natural number has a unique composition of prime factors obviously doesn't work if you could use 1 as a prime factor, too.

• @PSWorx said:

@intertravel said:

There is no explanation. It's simply a matter of definition. You can try explaining the consequences if 1 were prime, and hence the reason it's defined that way, but really it's just a matter of how the term 'prime' is defined - it excludes 1.

That doesn't solve anything, since the definition is pretty much tailor-made to excude 1 - it's easy to think up a different definition that contains all the intuitive properties of prime numbers but includes 1. (In fact, according to the wiki, 1 "was" a prime up until the 19th century, it only got changed when people began to find it ugly and cumbersome to write "all primes except 1" everywhere).

I think the suggestion of pointing out some consequences is a better one. I personally always found the example of prime factorization the most intuitive one - the whole idea that each natural number has a unique composition of prime factors obviously doesn't work if you could use 1 as a prime factor, too.

I have given him link to wiki page. I tell him that his maths teacher in school was wrong.

• @Nagesh said:

I have given him link to wiki page. I tell him that his maths teacher in school was wrong.

You can lead a horse to water, but you can't make him drink. Water, that is. You can make him drink beer. Which is HILARIOUS.

• Apparently "Drunk Horse" is a rock band, which is not funny at all

But then...

So you now, next time you get drunk, go home in a horse

• @blakeyrat said:

@Nagesh said:
I have given him link to wiki page. I tell him that his maths teacher in school was wrong.

You can lead a horse to water, but you can't make him drink. Water, that is. You can make him drink beer. Which is HILARIOUS.

i KNOW ONE SONG THAT GOES 'Whiskey for my men, beer for my horses'. strange rituel you got going there.

Looks like your connection to What the Daily WTF? was lost, please wait while we try to reconnect.