home *** CD-ROM | disk | FTP | other *** search
- Newsgroups: sci.math,sci.answers,news.answers
- Path: senator-bedfellow.mit.edu!bloom-beacon.mit.edu!spool.mu.edu!torn!watserv3.uwaterloo.ca!undergrad.math.uwaterloo.ca!neumann.uwaterloo.ca!alopez-o
- From: alopez-o@neumann.uwaterloo.ca (Alex Lopez-Ortiz)
- Subject: sci.math FAQ: Unsolved Problems
- Summary: Part 18 of many, New version,
- Originator: alopez-o@neumann.uwaterloo.ca
- Message-ID: <DI76LD.Fnt@undergrad.math.uwaterloo.ca>
- Sender: news@undergrad.math.uwaterloo.ca (news spool owner)
- Approved: news-answers-request@MIT.Edu
- Date: Fri, 17 Nov 1995 17:15:13 GMT
- Expires: Fri, 8 Dec 1995 09:55:55 GMT
- Reply-To: alopez-o@neumann.uwaterloo.ca
- Nntp-Posting-Host: neumann.uwaterloo.ca
- Organization: University of Waterloo
- Followup-To: sci.math
- Lines: 251
- Xref: senator-bedfellow.mit.edu sci.math:124392 sci.answers:3426 news.answers:57827
-
-
- Archive-Name: sci-math-faq/unsolvedproblems
- Last-modified: December 8, 1994
- Version: 6.2
-
-
-
-
-
-
- NAMES OF LARGE NUMBERS & UNSOLVED PROBLEMS
-
-
-
-
- _________________________________________________________________
-
- * Names of large numbers
- * Does there exist a number that is perfect and odd?
- * Collatz Problem
- * Goldbach's conjecture
- * Twin primes conjecture
-
- _________________________________________________________________
-
-
-
- Names of large numbers
-
-
- Naming for 10**k:
- k American European SI--Prefix
- -24 Yocto
- -21 Zepto
- -18 QUINTILLIONTH Atto
- -15 QUADRILLIONTH Femto
- -12 TRILLIONTH Pico
- -9 BILLIONTH Nano
- -6 MILLIONTH Micro
- -3 THOUSANDTH Milli
- -2 HUNDREDTH Centi
- -1 TENTH Deci
- 1 TEN Deca
- 2 HUNDRED Hecto
- 3 THOUSAND Kilo
- 4 Myria (?)
- 6 Million Million Mega
- 9 Billion Milliard Giga In italy (Thousand Milliards)
- 12 Trillion Billion Tera
- 15 Quadrillion Billiard Peta
- 18 Quintillion Trillion Exa
- 21 Sextillion Trilliard Zetta
- 24 Septillion Quadrillion Yotta
- 27 Octillion Quadrilliard
- 30 Nonillion Quintillion
- (Noventillion)
- 33 Decillion Quintilliard
- 36 UNDECILLION Sextillion
- 39 DUODECILLION Sextilliard
- 42 tredecillion Septillion
- 45 quattuordecillion Septilliard
- 48 quindecillion Octillion
- 51 sexdecillion Octilliard
- 54 septendecillion Nonillion
- (Noventillion)
- 57 octodecillion Nonilliard
- (Noventilliard)
- 60 novemdecillion Decillion
- 63 VIGINTILLION Decilliard
- 6*n (2n-1)-illion n-illion
- 6*n+3 (2n)-illion n-illiard
- 100 Googol Googol
- 303 CENTILLION
- 600 CENTILLION
- 10^100 Googolplex Googolplex
- The American system is used in:
- US,
- ...
- The European system is used in:
- Austria,
- Belgium,
- Chile,
- Germany,
- the Netherlands,
- Italy (see excepcion)
- hv@cix.compulink.co.uk (Hugo van der Sanden):
- To the best of my knowledge, the House of Commons decided to adopt the
- US definition of billion quite a while ago - around 1970? - since which
- it has been official government policy.
- dik@cwi.nl (Dik T. Winter):
- The interesting thing about all this is that originally the French used
- billion to indicate 10^9, while much of the remainder of Europe used
- billion to indicate 10^12. I think the Americans have their usage from
- the French. And the French switched to common European usage in 1948.
- gonzo@ing.puc.cl (Gonzalo Diethelm):
- Other countries (such as Chile, my own, and I think
- most of Latin America) use billion to mean 10^12, trillion to mean
- 10^18, etc. What is the usage distribution over the world population,
- anyway?
-
-
-
-
-
-
- _________________________________________________________________
-
-
-
- alopez-o@barrow.uwaterloo.ca
- Tue Apr 04 17:26:57 EDT 1995
-
-
- Does there exist a number that is perfect and odd?
-
-
-
- A given number is perfect if it is equal to the sum of all its proper
- divisors. This question was first posed by Euclid in ancient Greece.
- This question is still open. Euler proved that if N is an odd perfect
- number, then in the prime power decomposition of N , exactly one
- exponent is congruent to 1 mod 4 and all the other exponents are even.
- Furthermore, the prime occurring to an odd power must itself be
- congruent to 1 mod 4. A sketch of the proof appears in Exercise 87,
- page 203 of Underwood Dudley's Elementary Number Theory, 2nd ed. It
- has been shown that there are no odd perfect numbers < 10^(300) .
-
-
- _________________________________________________________________
-
-
-
- Collatz Problem
-
-
-
- Take any natural number m > 0 .
- n : = m;
- repeat
- if ( n is odd) then n : = 3*n + 1 ; else n : = n/2 ;
- until ( n = = 1 )
-
-
- Conjecture. For all positive integers m, the program above terminates.
-
-
-
-
- The conjecture has been verified up to 7 * 10^(11) .
-
-
-
- References
-
- Unsolved Problems in Number Theory. Richard K Guy. Springer, Problem
- E16.
-
-
-
-
-
-
- _________________________________________________________________
-
-
-
-
-
- Does there exist a number that is perfect and odd?
-
-
-
- A given number is perfect if it is equal to the sum of all its proper
- divisors. This question was first posed by Euclid in ancient Greece.
- This question is still open. Euler proved that if N is an odd perfect
- number, then in the prime power decomposition of N , exactly one
- exponent is congruent to 1 mod 4 and all the other exponents are even.
- Furthermore, the prime occurring to an odd power must itself be
- congruent to 1 mod 4. A sketch of the proof appears in Exercise 87,
- page 203 of Underwood Dudley's Elementary Number Theory. It has been
- shown that there are no odd perfect numbers < 10^(300) .
-
-
- _________________________________________________________________
-
-
-
- Collatz Problem
-
-
-
- Take any natural number m > 0 .
- n : = m;
- repeat
- if ( n is odd) then n : = 3*n + 1 ; else n : = n/2 ;
- until ( n = = 1 )
-
-
-
-
-
-
- The conjecture has been verified for all numbers up to 7 * 10^(11) .
-
-
-
- References
-
- Unsolved Problems in Number Theory. Richard K Guy. Springer, Problem
- E16.
-
-
-
- Elementary Number Theory. Underwood Dudley. 2nd ed.
-
-
-
-
- _________________________________________________________________
-
-
-
-
- Goldbach's conjecture
-
-
-
- This conjecture claims that every even integer bigger equal to 4 is
- expressible as the sum of two positive prime numbers. It has been
- tested for all values up to 2*10^(10) .
-
-
- _________________________________________________________________
-
-
- Twin primes conjecture
-
-
-
- There exist an infinite number of positive integers p with p and p + 2
- both prime. See the largest known twin prime section. There are some
- results on the estimated density of twin primes.
-
-
-
-
- _________________________________________________________________
-
-
-
-
-