16 (number)
natural number
16 (sixteen) is the natural number following 15 and preceding 17. It is the fourth power of two.
Mathematics
16 is the ninth composite number, and a square number: 42 = 4 × 4. It is the first fourth-power prime of the form p4: 16 = 24. It is the smallest number with exactly five divisors: 1, 2, 4, 8, and 16.
Sixteen is the only integer that equals mn and nm, for some unequal integers m and n (
m
=
4
{\displaystyle m=4}
,
n
=
2
{\displaystyle n=2}
, or vice versa). It has this property because
2
2
=
2
×
2
{\displaystyle 2^{2}=2\times 2}
. It is also equal to 32 (see tetration).
The aliquot sum of 16 is 15, within an aliquot sequence of four composite members (16, 15, 9, 4, 3, 1, 0) that belong to the prime 3-aliquot tree.
Sixteen is the largest known integer n, for which
2
n
+
1
{\displaystyle 2^{n}+1}
is prime.
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This entry incorporates text from “16 (number)” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.