Math Newsletter number 22; Wednesday, December 22, 2010.
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Archive is at

http://www2.stetson.edu/~efriedma/numbers.html

If you know a distinctive fact about a number not listed
efriedma@stetson.edu

http://www.goiit.com/posts/list/0/community-shelf-every-
number-is-special-78754.htm

http://www.numbergossip.com

1 is the multiplicative identity.
http://en.wikipedia.org/wiki/Identity_element

1 is the only positive integer that is neither prime nor
composite
http://www.numbergossip.com/1

2 is the only even prime.
http://www.blurtit.com/q228557.html

2 is the smallest positive prime number.
http://www.numbergossip.com/2

For any polyhedron, 2 is the number of vertices plus the
number of faces minus the number of edges.
http://www.mathsisfun.com/geometry/vertices-faces-edges.html

3 is the number of spatial dimensions we live in.
http://en.wikipedia.org/wiki/Dimension
http://news.softpedia.com/news/What-Are-the-Spatial-
Dimensions-16390.shtml

3 is the greatest number of consecutive integers that can be
pairwise relatively prime.
http://primes.utm.edu/glossary/xpage/PairwiseRelativelyPrime.
html

3 is the only prime sandwiched between a prime and a
composite number.
http://primes.utm.edu/curios/page.php/3.html

3 is the only prime followed by a square.
http://mathworld.wolfram.com/Near-SquarePrime.html

Every positive integer is the sum of at most 3 triangular
numbers.
http://mathworld.wolfram.com/TriangularNumber.html

4 is the smallest number of colors sufficient to color all
planar maps.
http://en.wikipedia.org/wiki/Four_color_theorem

4 is the only positive number that is both the sum and the
product of the same two integers.

Are you sure that 2 plus 2 is equal to 2 times 2?

by "Yarnlady is happy every day" on April 6th, 2008

Let's see: here's two xx

and here's two more xx

So how many times did I put two xx on the page? Two times.

so xx plus xx is 4 (xxxx)

and two times xx is (goes back and counts them xx xx)

Wow, 4.

4 is the order of the smallest non-cyclic group (submitted by
Sam Steingold).
http://en.wikipedia.org/wiki/List_of_small_groups

Every positive integer is the sum of at most 4 squares.
http://en.wikipedia.org/wiki/Waring%27s_problem

4 is the only composite number that is equal to the sum of
its prime factors.
http://www.wordiq.com/definition/Four

4 is the only composite number n which doesn't divide (n-1)!
http://www.physicsforums.com/archive/index.php/t-349819.html

5 is the number of Platonic solids.
http://en.wikipedia.org/wiki/Platonic_solid

6 is the smallest perfect number.
http://en.wikipedia.org/wiki/Perfect_number

6 is the order of the smallest nonabelian (non commutative)
group.
http://en.wikipedia.org/wiki/List_of_small_groups

7 is the smallest number of faces of a regular polygon that
is not constructible by straightedge and compass.
http://en.wikipedia.org/wiki/Constructible_polygon

8 is the largest cube in the Fibonacci sequence.
http://mathoverflow.net/questions/1624/is-8-the-largest-
cube-in-fibonacci-sequence

9 is the maximum number of cubes that are needed to sum to
any positive integer.
http://en.wikipedia.org/wiki/Waring%27s_problem

9 is the smallest odd positive composite integer.
http://www.numbergossip.com/9

10 is the base of our number system.
http://ideonexus.com/2008/07/08/why-a-base-10-number-system/

10 is the smallest product of two non-consecutive primes.
Contributed by Cris Stringfellow