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16 (sixteen) is the natural number following 15 and preceding 17. 16 is a composite number, and a square number, being 42 = 4 × 4. It is the smallest number with exactly five divisors, its proper divisors being , , and . In speech, the numbers 16 and 60 are often confused. When carefully enunciated, they differ in which syllable is stressed: 16 vs 60 . However, in dates such as 1666 or when contrasting numbers in the teens, such as ''15, 16, 17,'' the stress shifts to the first syllable: 16 . Sixteen is the fourth power of two. For this reason, 16 was used in weighing light objects in several cultures. The British have 16 ounces in one pound; the Chinese used to have 16 ''liangs'' in one ''jin''. In old days, weighing was done with a beam balance to make equal splits. It would be easier to split a heap of grains into sixteen equal parts through successive divisions than to split into ten parts. Chinese Taoists did finger computation on the trigrams and hexagrams by counting the finger tips and joints of the fingers with the tip of the thumb. Each hand can count up to 16 in such manner. The Chinese abacus uses two upper beads to represent the 5s and 5 lower beads to represent the 1s, the 7 beads can represent a hexadecimal digit from 0 to 15 in each column. == In mathematics == As a power of 2 it has an aliquot sum one less than itself, 15; and is the fifth composite member of the 3-aliquot tree having the 7 member aliquot sequence (16, 15, 9, 4, 3, 1, 0). Sixteen is the first number to be the aliquot sum of a lesser number, 12; it is also the aliquot sum of the greater number; the discrete semiprime, 26. It is the fourth power of two. Sixteen is the only integer that equals ''m''''n'' and ''n''''m'', for some unequal integers ''m'' and ''n'' (''m'' = 4, ''n'' = 2, or vice versa). It has this property because 22 = 2 × 2. It is also equal to 32 (see tetration). 15 and 16 form a Ruth–Aaron pair under the second definition in which repeated prime factors are counted as often as they occur. Since it is possible to find sequences of 16 consecutive integers such that each inner member shares a factor with either the first or the last member, 16 is an Erdős–Woods number. The smallest such range of 16 consecutive integers is from 2184 to 2200.〔R. K. Guy, ''Unsolved Problems in Number Theory'' New York: Springer-Verlag (2004): B28〕 In bases 20, 24 and 30, sixteen is a 1-automorphic number (displayed as the numeral 'G'). 16 is a centered pentagonal number 16 is the base of the hexadecimal number system, which is used extensively in computer science 16 appears in the Padovan sequence, preceded by the terms 7, 9, 12 (it is the sum of the first two of these) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「16 (number)」の詳細全文を読む スポンサード リンク
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