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
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
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)
4 is the order of the smallest non-cyclic group (submitted by
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