Math Newsletter number 22; Wednesday, December 22, 2010.
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What's Special About This Number?

If you know a distinctive fact about a number not listed
here, please e-mail me.

0 is the additive identity.

1 is the multiplicative identity.

1 is the only positive integer that is neither prime nor

2 is the only even prime.

2 is the smallest positive prime number.

For any polyhedron, 2 is the number of vertices plus the
number of faces minus the number of edges.

3 is the number of spatial dimensions we live in.

3 is the greatest number of consecutive integers that can be
pairwise relatively prime.

3 is the only prime sandwiched between a prime and a
composite number.

3 is the only prime followed by a square.

Every positive integer is the sum of at most 3 triangular

4 is the smallest number of colors sufficient to color all
planar maps.

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).

Every positive integer is the sum of at most 4 squares.

4 is the only composite number that is equal to the sum of
its prime factors.

4 is the only composite number n which doesn't divide (n-1)!

5 is the number of Platonic solids.

6 is the smallest perfect number.

6 is the order of the smallest nonabelian (non commutative)

7 is the smallest number of faces of a regular polygon that
is not constructible by straightedge and compass.

8 is the largest cube in the Fibonacci sequence.

9 is the maximum number of cubes that are needed to sum to
any positive integer.

9 is the smallest odd positive composite integer.

10 is the base of our number system.

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