Prime Numbers

[Kyle]

First off- I hate prime numbers. They're bad for OCD.

But second- I was on my way in to work today and thought, "How can you tell if large numbers are prime without having to try every number less than it?"

So thanks to the glorious internet- I found .

He explains the simple rules pretty clearly (and I'm sure there are other, more complicated ones he doesn't provide). But here's the shorthand:

1- Take the square root of the number and drop the decimals.

2- Try to divide the number by the prime numbers equal to or less than the number you got in step one.

3- If none of them divide easily- it's prime!

Example: 137.

1- The square root is 11.704.
2- The primes we need to check are 2, 3, 5, 7 and 11.
3- None of those divide evenly, so it's prime!

Maybe all of y'all knew this, but I thought it was cool shorthand.

[Zen]

Cool! I'll have to pass that on to my math geek children and have them look at me like I'm an idiot because they already knew it! (Oh, yeah, my son decided to double major in Engineering and Math...)

[Mike]

Prime numbers neither good nor bad solely by dint of their primeness. Many of the numbers that I find attractive are prime, and my most favorite numbers (23.13, 7) are all prime. But there are ugly and unattractive primes as well. 31? Gross. 127? Not a fan.

On the other hand, 36 is not just a composite number, but a super-composite, and it's absolutely beautiful. Kyle, I'm sure your OCD LOVES 36, and I'm right there with you. That's a great number. 91? Product of 7 and 13... I love 91. But 299? Product of 13 & 23... 299 is just disturbing. It's just one off of 300 (which is a great number) and feels like it should really be prime, but isn't. It bugs me.

1001. Another really good number. Not at all prime, although it feels like it should be (it's actually 7 x 11 x 13). But it's symmetrical and palindromic in it's construction, so it just looks good, in addition to having cool properties.

4 is useful and hardworking. And I always associate 4 with you. I think 4 was your favorite number as a kid.

Huh. I have strong feelings about numbers.

[Kyle]

[Mike]

So powers of 2 with exponents that are also powers of 2 would clearly be the bestest of all?

2, 4, 16, 256, 65536...

Although anything beyond 1024 is probably getting too unwieldy.

[Kyle]

[Mike]

How about 2048? It is a power of 2, it has 4 digits, and all of its digits are ALSO powers of 2.

[Kyle]

[Mike]

I actually wondered about the zero, because I also just considered it a placeholder that didn't really count.

[Eliahad]

I like lamp.

I mean 19. 19 is the best of numbers.

[Mike]

Go talk about music and wine, ya hippie.

[Elle]

Lord is the purpose of this entire thread to troll me? I need to go hide alone in darkness, and btw, you are all dirty heathens and hippies.

[Kyle]

As much as what I've posted sounds like a joke, Elle- it's all true.

[Elle]

Well, if your preferences about numbers don't interfere with life in any bothersome way, then hey, roll with it. And if they come without color, so much the better. This type of thing can creep up on you though, especially if you have anxieties. I like to think about ugly-seeming numbers and irregularities and do things a very wrong-seeming number of times. A little touch of ocd feeling is no problem or even entertains us, but needs retraining if it's more than that. And all of those feelings are totally retrainable.

[Elle]

As a for instance, without being aware of it at all, I posted that at 9:28, because parts of the brain that aren't in command want to be in command, and they act in inscrutable ways to make things happen the way they think makes sense. It has to be fought deliberately when that happens.