ITT: Numbers that feel like they should be prime, but aren't

221
1001

60 and 5040

1

Grothendieck was one of the most abstract thinkers in mathematics.

His revolutionary treatises EGA and SGA total approximately 10,000 pages, and in all of that contain only a single example.

2

any industrial-grade prime which is composite

This has got to be a troll thread.

1

Bait or retard?

Is pie a prime?
You can certainly eat a slice of it.

It seems like [math]119+41\sqrt{7} [/math] should be prime in the unique factorization domain [math]\mathbb{Z}[\sqrt{7}][/math].

...

5041

Why does it seem prime to you?

8231111

It was more like a joke about we (or at least I) have almost no intuition for primality in algebraic extensions.

A number theorist might have some intuition.

284328329121231231879948359839548439853848914387428347283748237847283463344727342727777272993495322042034010300410100400104001000400104003002304020304004

We always have a laugh in math lab about that one, it's so obvious.

I want to factor expressions like [math]119+41\sqrt{7}[/math] over [math]\mathbb{Z}[7][/math] using wolframalpha.

A brief google search revealed that it can do this provided input formatted as such: reference.wolfram.com/language/tutorial/PolynomialsOverAlgebraicNumberFields.html

However, when I try this, it just gets confused.

Help?

*Meant [math]\mathbb{Z}[\sqrt{7}][/math], obviously.

The first step is to stop using Wolfram Alpha. You should be able to figure it out from there.

>3 divides both 10 and 9.
>3 divides 10

I'm not sure that feature is what you want to be using for this. You're trying to factor an algebraic integer, not polynomials. This would be akin to trying to get prime factorizations of integers by finding roots of rational polynomials.

>3 divides both 10 and 9

sometimes i don't know whether i hate this board or love this board

[math]\pi[/math]

>feels like a prime
>3 divides both 10 and 9
>60 and 5040

Wow.
salutes you.
You should stop by and tutor us

15 and 21

GET OUT OF HERE NORMIE!!!!!

111 does sort of feel like it should be prime

Yeah. Start using an actual programming language. Like VBA.

Kappa.

Come on, any number with a digitsum of 3 is divisible by 3.

So 111 does most certainly not feel in any way like it should be prime.

Summerfags.....

en.wikipedia.org/wiki/Divisibility_rule

2545841453

>5040
>7 fucking factorial
kek

It was obviously a typo you fucking spergs.

Is no one else curious why someone dedicated a whole website to pictures of numbers?

I think he meant that 3 divides into 30 to make 10

>and in all of that contain only a single example.
Source? Sounds insane

How the fucking fuck does 39 feel like it should be prime when all digits are multiples of 3?
these
yea also 39058320627692063557

My post number should be

what the fuck did i () tell u !?!?!?!?!

91
fuck 91

...

Even numbers can't be prime. I'm m is any integer then 2m is always even.

53

>Even numbers can't be prime
That's not true.

I bet you think 1 is prime too.

0 and 2 are prime

0 is not prime

Of course it is. If a and b are integers such that ab = 0, then a or b is divisible by 0, just like for all other primes.

this is the shittiest fucking thread I've ever seen

It is prime in the integers, and can in fact fail to be prime in other rings. Whether or not a ring has zero divisors (whether 0 is prime) is actually really important.

>all digits share a common divisor
>doesn't feel prime
I bet you're the type of guy who doesn't find e^(i*pi)=-1 painfully obvious

This. I'm gonna bail out.

Die in a fire all of you

1

check those primes post numbers

>divisible by zero
salutes you

2 but it's an even number so it can't be one.

>gets triggered by hearing 0 and divisible in the same sentence
You know something's up, but you don't quite know what. And it shows.

i love it when someone who actually knows math sets up a honeypot like this and retards fall right into it.

>feel like it should be
>tries to prove it
>denies
are you fucking retarded my mane ?

In the reverse, I look at 97 and feel like it shouldn't be prime but it is

no he meant 3 divides both 30 and 9 as in

39 = 30 + 9 = 3(10 + 3)

Any integer with more than one digit whose digits are all identical is composite.

Which is the easier way to tell, but of course that's just a special case of finding a number that divides every digit

The thing about prime looking non-primes is that they almost have to be divisible by a two-digit number, because otherwise it's too easy to check for divisors. Secondly, it cannot be too big, or the intuition goes out the window, and it's not convincingly prime enough. Can't have too many prime divisors either, clearly.
Being divisible by 11 is an obvious nono, 17 is too big, so you have to be divisible by 13. The lowest prime-looking non-prime divisible by 13 is 91. This is why, to me, 91 is the ultimate non-prime prime, with 49 being a distant second.

11

Nice quads

And whose absolute value is greater than 11. Fuck

Why (I'm asking about the 111111 ones, obviously).

ITT now: numbers that don't look prime but are

2

Okay, so it's not true for 1. The second repunit prime has 19 digits. But for other digits it's true

The number mentions is pretty surprising

The proof that all repdigits which are not repunits are composite is trivial.

2^5

/thread