In Mathematics
Fourteen is a composite number, its divisors being 1, 2, 7 and 14.
14 is the 3rd discrete semiprime (2.7) and the 3rd member of the (2.q) discrete semiprime family. The number following 14 —15— is itself a discrete semiprime and this is the first such pair of discrete semiprimes. The next example is the pair commencing 21.
The aliquot sum σ(n) of 14 is 10, also a discrete semiprime and this is again the first example of a discrete semiprime having an aliquot sum in the same form. 14 has an aliquot sequence of 6 members (14,10,8,7,1,0) 14 is the third composite number in the 7-aliquot tree.
Fourteen is itself the Aliquot sum of two numbers; the discrete semiprime 22, and the square number 196.
Fourteen is the base of the tetradecimal notation.
In base fifteen and higher bases (such as hexadecimal), fourteen is represented as E.
Fourteen is the sum of the first three squares, which makes it a square pyramidal number.
This number is the lowest even n for which the equation φ(x) = n has no solution, making it the first even nontotient (see Euler's totient function).
14 is a Catalan number, the only semiprime among all Catalan numbers.
Take a set of real numbers and apply the closure and complement operations to it in any possible sequence. At most 14 distinct sets can be generated in this way. This holds even if the reals are replaced by a more general topological space. See Kuratowski's closure-complement problem.
Fourteen is a Keith number in base 10: 1, 4, 5, 9, 14, 23, 37, 60, 97, 157...
Fourteen is an open meandric number.
Fourteen is a Companion Pell number.
According to the Shapiro inequality 14 is the least number n such that there exist such that
where .
There are fourteen possible Bravais lattices that fill three-dimensional space.
The cuboctahedron, the truncated cube, and the truncated octahedron each have fourteen faces. The rhombic dodecahedron, which tessellates 3-dimensional space and is the dual of the cuboctahedron, has fourteen vertices. The truncated octahedron, which also tessellates 3-dimensional space, is the only permutohedron.
Read more about this topic: 14 (number)
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