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Old 2008-09-30, 21:39   #1
Prime95
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Default Odd email

I received this email today. The number is not prime, anyone have other ideas?


A senior ranking Non Commissioned Officer here in Iraq has given a group of us a number and no clues to as to what it is. A few of us feel it is something to do with it being a prime number. We are all not math geniuses. So here is where I turn to you for your expert opinion. The number is:

20120121122515626145776622735224615338815731191617

Please assist in any way you can. Thanks for your help.
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Old 2008-09-30, 21:43   #2
Mini-Geek
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BTW its factorization is:
20120121122515626145776622735224615338815731191617 = 479 * 133289810174980013 * 315136079611630044400219008571

Just from looking at the number I see it has a quite high number of pairs of digits (...1122...776622 etc.), but in a number of this length, that could be purely coincidental.
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Old 2008-10-01, 03:52   #3
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Well, looking at it as a substitution cipher, I get the possibilities:

Code:
20120	tat
1211225	lkve	lkby	laly	lalbe	laave
	auly	auve	abkve	abkbe	abaly	abaave	abalbe
15	o	ae
6	f
26	z	bf
14	n	ad
5	e
7	g
7	g
6	f
22	v	bb
7	g
3	c
5	e
224	vd	bx	bbd
6	f
15	o	ae
3	c
3	c
8	h
8	h
15	o	ae
7	g
3	c
119	ki	
16	p	af
17	q	ag
which seems like gibberish in English, though isn't necessarily English even if it is a cipher...

I initially thought it could be a cipher because of the many strings of 2x and 1x in the first half.

Within the number, only
2012012112251562614577662273522461533881
120121122515626145776622735224615338815731191617
6145776622735224615338815731191617
617
17
7
are prime (working from the beginning to end or vice versa, deleting one digit at a time). This is quite a bit lower than most that I've seen (ie from the Homeprime patterns).

I don't know if this is helpful at all, but good luck with it
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Old 2008-10-01, 22:58   #4
Orgasmic Troll
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Quote:
Originally Posted by Mini-Geek View Post
BTW its factorization is:
20120121122515626145776622735224615338815731191617 = 479 * 133289810174980013 * 315136079611630044400219008571

Just from looking at the number I see it has a quite high number of pairs of digits (...1122...776622 etc.), but in a number of this length, that could be purely coincidental.
back-of-the-envelope calculation:

50 digit number has 49 pairs of digits, the probability that a pair of digits is comprised of the same digit is 10%, so we expect to see about 5 pairs (which includes something like ...12223... counting as 2 pairs).

I count 9 pairs, which is 1.95 standard deviations away (using the binomial distribution), and I think that's right under the 95% confidence interval, so I'd say it's not extraordinary, but I wouldn't be surprised if someone else came along and told me I was wrong
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Old 2008-11-02, 15:55   #5
Flatlander
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Okay, I give up.
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Old 2008-11-17, 18:44   #6
m_f_h
 
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Quote:
Originally Posted by Prime95 View Post
I received this email today. The number is not prime, anyone have other ideas?
20120121122515626145776622735224615338815731191617
I inserted commas as to get numbers between 01 and 26, but in the resulting text I only saw "egg". Upon rot13, I see SMART and other stuff.
Code:
? [20,12,01,21,12,25,15,6,26,14,5,7,7,6,6,22,7,3,5,22,4,6,15,3,3,8,8,15,7,3,11,9,16,17]
? Strchr(Vecsmall(%+vector(#%,i,64)))
"TLAULYOFZNEGGFFVGCEVDFOCCHHOGCKIPQ"
/*pasted into rot13 */
GYNHYLBSMARTTSSITPRIQSBPPUUBTPXVCD
What's the probability of /accidentally/ getting "SMART", using two elementary/natural encoding methods (# of letter in the alphabet, and rot13) ?

PS: I used the "maximum munch principle" for putting the commas, but maybe military people are less scientific and some other splitting up was intended - I didn't check if something more reasonable can be obtained.
PPS: first I was intrigued by the repetition at the beginning and tried direct ascii conversion using maximum munch principle: 201,201,211,225,156,... but this gives nothing afaics ; b.t.w. it is improbable that the message starts with 2 repeated letters (unless it is to be read from right to left).

Last fiddled with by m_f_h on 2008-11-17 at 18:53
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Old 2008-11-18, 12:22   #7
hhh
 
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The other question is: Do we really want to help officers in Iraq, commissioned or not, help doing their work? I would not, even if I was not too lazy to think about puzzles with no clue whatsoever.

Oops, did I just annihilate my chance of ever getting a visa for the States? H.
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Old 2008-11-19, 03:56   #8
Orgasmic Troll
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Quote:
Originally Posted by m_f_h View Post
[/code]What's the probability of /accidentally/ getting "SMART", using two elementary/natural encoding methods (# of letter in the alphabet, and rot13) ?
The chances of getting "SMART"? Infinitesimally small. The chances of getting a 5 letter English word?

29 different five letter sequences (incorrectly assuming independence), roughly 8600 5 letter words in the English language, the chances of NONE of the sequences containing a word is (1-8600/26^5)^29

...so about 1 out of 50.

(if you don't like my independence assumption, we can take the 7 different blocks of letters that don't interact for a lower bound. That gives us about 1 out of 200)

Last fiddled with by Orgasmic Troll on 2008-11-19 at 03:59
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Old 2008-11-21, 16:10   #9
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A possible clue:


The first 11 digits are all 0, 1 or 2.


Digit counts:

0 appears 2 times
1 appears 12 times
2 appears 10 times
3 appears 4 times
4 appears 2 times
5 appears 6 times
6 appears 6 times
7 appears 5 times
8 appears 2 times
9 appears 1 time

There is a rather uneven distribution of digits, and most digits appear an even number of times. Of course all of this could be chance...

Last fiddled with by 10metreh on 2008-11-21 at 16:21
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Old 2008-11-21, 17:49   #10
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A) Since there are 50 digits, I spread them out in rows of 5:

Code:
A)          B)   C)
2 0 1 2 0   VA   2 0 1 2 0
1 2 1 1 2   NY   1 - - - -
2 5 1 5 6   WV   2 - - - -
2 6 1 4 5   WV   2 - - - -
7 7 6 6 2   TX   7 - - - -

2 7 3 5 2   NC   2 - - - -
2 4 6 1 5   VA   2 - - - -
3 3 8 8 1   FL   3 - - - -
5 7 3 1 1   SD   5 7 3 1 1
9 1 6 1 7   CA   9 1 6 1 7
B) Since five of the ten groups started with '2', I began to think of zip codes. (All the zip codes around Wash DC start with 2, so this stood out). So, I put the state letters beside each group of 5.

C) I fed them into a zip code lookup function, forwards, backwords, down, and up, but only found 5 valid codes (out of 40):

Forwards:
20120 ... ... Sully Station:Fairfax:VA
57311 ... ... Farmer:Hanson:SD
91617 ... ... Valley Village:Los Angeles:CA

Backwords: nothing

Down:
21227 ... ... Baltimore:Baltimore:MD

Up:
95322 ... ... Santa Nella:Merced:CA

Diagonals: nothing

I found it really peculiar that the only digits that made valid zip codes were along the top, left, and bottom of my chart. I'm sure it's just coincidence though.

I don't have any more zip code ideas. I'm posting here to possibly spur someone else on

Last fiddled with by uigrad on 2008-11-21 at 17:55 Reason: typo
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Old 2008-11-25, 22:33   #11
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It's kind of odd that the number starts with a 2, then two entries of 012.

I wonder if somebody left out some character code indicator, e.g.:
2 0x12 0x12 1122515626145776622735224615338815731191617

Now, 12 could be a form feed character; or it could be the size of something.

Removed speculation that didn't add up...

OK, I give up for now.

Last fiddled with by Ken_g6 on 2008-11-25 at 22:38 Reason: Removed speculation that didn't add up...
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