14
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Number
$14$ (fourteen) is:
- $2 \times 7$
- The $1$st power of $14$ after the zeroth $1$:
- $14 = 14^1$
- The $1$st positive integer solution to $\map {\sigma_1} n = \map {\sigma_1} {n + 1}$:
- $\map {\sigma_1} {14} = 24 = \map {\sigma_1} {15}$
- where $\sigma_1$ denotes the divisor sum function
- The $1$st nontotient:
- $\nexists m \in \Z_{>0}: \map \phi m = 14$
- where $\map \phi m$ denotes the Euler $\phi$ function
- The $1$st Keith number:
- $1$, $4$, $5$, $9$, $14$, $\ldots$
- The $2$nd integer after $1$ whose divisor sum divided by its Euler $\phi$ value is a square:
- $\dfrac {\map {\sigma_1} {14} } {\map \phi {14} } = \dfrac {24} 6 = 4 = 2^2$
- The $3$rd square pyramidal number after $1$, $5$:
- $14 = 1 + 4 + 9 = \dfrac {3 \paren {3 + 1} \paren {2 \times 3 + 1} } 6$
- The $3$rd positive integer after $1$, $3$ of which the product of its Euler $\phi$ function and its divisor count equals its divisor sum:
- $\map \phi {14} \map {\sigma_0} {14} = 6 \times 4 = 24 = \map {\sigma_1} {14}$
- The $1$st of the $4$th pair of consecutive integers whose product is a primorial:
- $14 \times 15 = 210 = 7 \#$
- The $4$th Catalan number after $(1)$, $1$, $2$, $5$:
- $14 = \dfrac 1 {4 + 1} \dbinom {2 \times 4} 4 = \dfrac 1 5 \times 70$
- The number of different representations of $1$ as the sum of $4$ unit fractions.
- The $5$th semiprime after $4$, $6$, $9$, $10$:
- $14 = 2 \times 7$
- The $6$th integer $m$ such that $m! - 1$ (its factorial minus $1$) is prime:
- $3$, $4$, $6$, $7$, $12$, $14$
- The $6$th and last after $1$, $2$, $5$, $6$, $10$ of $6$ integers $n$ such that the alternating group $A_n$ is ambivalent
- The $7$th even number after $2$, $4$, $6$, $8$, $10$, $12$ which cannot be expressed as the sum of $2$ composite odd numbers.
- The $9$th positive integer after $2$, $3$, $4$, $7$, $8$, $9$, $10$, $11$ which cannot be expressed as the sum of distinct pentagonal numbers.
- The $11$th after $1$, $2$, $3$, $4$, $5$, $6$, $7$, $8$, $10$, $12$ of $21$ integers which can be represented as the sum of two primes in the maximum number of ways
- The $12$th (strictly) positive integer after $1$, $2$, $3$, $4$, $6$, $7$, $8$, $9$, $10$, $12$, $13$ which cannot be expressed as the sum of distinct primes of the form $6 n - 1$
- The $12$th integer $n$ after $0$, $1$, $2$, $3$, $4$, $5$, $6$, $7$, $8$, $9$, $13$ such that $2^n$ contains no zero in its decimal representation:
- $2^{14} = 16 \, 384$
- There exist $14$ distinct Bravais lattices.
Kuratowski's Closure-Complement Problem
Let $T = \struct {S, \tau}$ be a topological space.
Let $A \subseteq S$ be a subset of $T$.
By successive applications of the operations of complement relative to $S$ and the closure, there can be as many as $14$ distinct subsets of $S$ (including $A$ itself).
Arithmetic Functions on $14$
\(\ds \map {\sigma_0} { 14 }\) | \(=\) | \(\ds 4\) | $\sigma_0$ of $14$ | |||||||||||
\(\ds \map \phi { 14 }\) | \(=\) | \(\ds 6\) | $\phi$ of $14$ | |||||||||||
\(\ds \map {\sigma_1} { 14 }\) | \(=\) | \(\ds 24\) | $\sigma_1$ of $14$ |
Also see
- Kuratowski's Closure-Complement Problem
- 14 Distinct Bravais Lattices
- 12 times Divisor Sum of 12 equals 14 times Divisor Sum of 14
- Previous ... Next: Integers whose Phi times Divisor Count equal Divisor Sum
- Previous ... Next: Representation of 1 as Sum of n Unit Fractions
- Previous ... Next: Positive Even Integers not Expressible as Sum of 2 Composite Odd Numbers
- Previous ... Next: Integers whose Number of Representations as Sum of Two Primes is Maximum
- Previous ... Next: Sequence of Integers whose Factorial minus 1 is Prime
- Previous ... Next: Integers not Expressible as Sum of Distinct Primes of form 6n-1
- Previous ... Next: Powers of 2 with no Zero in Decimal Representation
Historical Note
The two main occurrences of the number $14$ of contemporary social significance are:
- the number of pounds avoirdupois in one stone
- the number of days in the fortnight.
Sources
- 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): Glossary
- 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $14$
- 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): Glossary
- 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $14$
- 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): crystallography
- 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): crystallography