Number Gossip

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Unique Properties of 11

11 is the smallest prime such that 2^p-1 is not prime
11 is the largest number which is not expressible as the sum of two composite numbers
The first five rows of Pascal's triangle, when read left-to-right, form the first five powers of 11
11 is the smallest prime for which the sum of digits equals the number of digits
11 hexominoes can be folded into a cube
11 is the only prime comprising an even number of identical digits
11 is the smallest strobogrammatic prime
11 is the only palindromic prime with an even number of digits
There are 11 convex uniform tilings (regular and semiregular) of the Euclidean plane. By symmetry there are 11 Archimedean (all edge lengths are the same, and all vertices look alike) tilings of the plane
11 is the only prime whose period length is two
11 divides all palindromes with an even number of digits
The diagonals of a regular pentagon divide it into 11 regions
11 is the number of 2 by 2 binary matrices M such that M² is also a binary matrix
11 is the smallest pandigital number in base 3: it is 102 in base 3 and contains all the possible digits
11 is the smallest prime with no prime digits
11 is the smallest multidigit number whose digital sum is prime
11 is the first prime repunit
11 is the smallest strong prime, aka a prime number that is greater than the arithmetic mean of its prime neighbors
11 is the largest known multiplicative persistence

Odd

Prime

Twin

Ulam