You are not logged in.

- Topics: Active | Unanswered

**mathgogocart****Member**- Registered: 2012-04-29
- Posts: 1,424

We will post prime numbers and say something intrssting about the number

So lets start

3!

the unluck number:|:|:|:|

Hey.

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 14,801

2-the only even prime.

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

Offline

**mathaholic****Member**- From: Juliania
- Registered: 2012-11-29
- Posts: 2,797
- Website

5-number of fingers on your hand!!!

"Double the fun, double the thrill, double the coolness" - Julianthewiki

Offline

**noelevans****Member**- Registered: 2012-07-20
- Posts: 236

7 One of the few primes whose reciprocal is easy to remember.

For 1/7: 2*7=14, 2*14=28, 2*28+1=57 ; that is, keep doubling the denominator till you reach

56 then add the numerator to the 56 to get the last two digits of 1/7 which is a repeating .142857.

Of course 1/2, 1/3, 1/5 and 1/11 aren't bad either.

Writing "pretty" math (two dimensional) is easier to read and grasp than LaTex (one dimensional).

LaTex is like painting on many strips of paper and then stacking them to see what picture they make.

Offline

**mathaholic****Member**- From: Juliania
- Registered: 2012-11-29
- Posts: 2,797
- Website

13- number of different cards in a deck

"Double the fun, double the thrill, double the coolness" - Julianthewiki

Offline

**noelevans****Member**- Registered: 2012-07-20
- Posts: 236

11 --- one of the few primes larger than 10 that it is easy to multiply by. To multiply a number, say

3142 by 11 just put a zero in front and behind it, like so 031420 and then add consecutive pairs of

digits (typically from right to left since in some cases there may be carries) and record these sums:

0+3, 3+1, 1+4, 4+2, 2+0 ; that is, 34562. If a sum exceeds 9 then carry 1 to the next sum for example 23572 ---> 0235720 ---> 2 5 8 12 9 2 = 2 5 9 2 9 2; that is, 259292 carrying the 1

from the 12 into the 8 in the next column to the left. With a little practice this can be done quickly

in one's head.

*Last edited by noelevans (2012-12-06 10:55:06)*

Writing "pretty" math (two dimensional) is easier to read and grasp than LaTex (one dimensional).

LaTex is like painting on many strips of paper and then stacking them to see what picture they make.

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 14,801

19-the first prime with the sum of its digits equal to 10.

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 81,367

23

John Forbes Nash's favorite prime number.

I have the result, but I do not yet know how to get it.

All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 14,801

Boy, was that guy an ugly fellow!

97-largest prime below 100.

Here lies the reader who will never open this book. He is forever dead.

Offline

**mathgogocart****Member**- Registered: 2012-04-29
- Posts: 1,424

131-the number that is ALSO PSELLED BCAKWARDS...OMG

Hey.

Offline

**noelevans****Member**- Registered: 2012-07-20
- Posts: 236

13 --- a baker's dozen.

Writing "pretty" math (two dimensional) is easier to read and grasp than LaTex (one dimensional).

LaTex is like painting on many strips of paper and then stacking them to see what picture they make.

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 14,801

23-number of characters in "greengrocers apostrophe"

Here lies the reader who will never open this book. He is forever dead.

Offline

**noelevans****Member**- Registered: 2012-07-20
- Posts: 236

Three digit numbers with two 3's and one 1 or with two 1's and one 3. Only one of them is NOT a

prime.

LaTex is like painting on many strips of paper and then stacking them to see what picture they make.

Offline

**noelevans****Member**- Registered: 2012-07-20
- Posts: 236

2 --- the only number for which any positive integer can be written as a sum of non-negative powers of that number alone using each power of the number no more than once.

LaTex is like painting on many strips of paper and then stacking them to see what picture they make.

Offline

**mathgogocart****Member**- Registered: 2012-04-29
- Posts: 1,424

101-1-1=0-the first sensible number

Hey.

Offline

**mathaholic****Member**- From: Juliania
- Registered: 2012-11-29
- Posts: 2,797
- Website

My answer

*Last edited by julianthemath (2012-12-13 18:05:18)*

"Double the fun, double the thrill, double the coolness" - Julianthewiki

Offline

**mathgogocart****Member**- Registered: 2012-04-29
- Posts: 1,424

111 3 digits repeated trpile

Hey.

Offline

**mathaholic****Member**- From: Juliania
- Registered: 2012-11-29
- Posts: 2,797
- Website

Mathgogocart, 111 is not prime. It is divisible by 1, 3, 37, 111 (ay be incomplete).

"Double the fun, double the thrill, double the coolness" - Julianthewiki

Offline

**mathgogocart****Member**- Registered: 2012-04-29
- Posts: 1,424

2

Hey.

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 81,367

I think you already picked 2.

101 - a room with a special meaning.

I have the result, but I do not yet know how to get it.

All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Offline

**mathaholic****Member**- From: Juliania
- Registered: 2012-11-29
- Posts: 2,797
- Website

bobbym wrote:

101 - a room with a special meaning.

What is the special meaning?

17-the sum of the first four primes.

"Double the fun, double the thrill, double the coolness" - Julianthewiki

Offline

**scientia****Member**- Registered: 2009-11-13
- Posts: 222

According to the Old Testament, **31** kings were defeated by Joshua after the children of Israel had crossed the river Jordan (Joshua 12:924).

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 81,367

1111111111111111111

The second repunit that is prime.

julianthemath wrote:

What is the special meaning?

You are a little young yet but some day you will read 1984.

I have the result, but I do not yet know how to get it.

All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Offline

**mathaholic****Member**- From: Juliania
- Registered: 2012-11-29
- Posts: 2,797
- Website

Oh, okay.

113-the 30th prime.

"Double the fun, double the thrill, double the coolness" - Julianthewiki

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 81,367

11111111111111111111111 the 3rd repunit that is a prime.

I have the result, but I do not yet know how to get it.

All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Offline