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25-422: (Redirected from Ninety ) 90 may refer to: 90 (number) one of the years 90 BC , AD 90 , 1990 , 2090 , etc. 90 (album) , an album by the electronic music group 808 State 90 (EP) , an album by the band South Club Atomic number 90: thorium 90 Antiope , double asteroid in the outer asteroid belt Vehicles [ edit ] Audi 90 ,

50-686: A sudoku puzzle with a unique solution is 17. 17 is the least k {\displaystyle k} for the Theodorus Spiral to complete one revolution . This, in the sense of Plato , who questioned why Theodorus (his tutor) stopped at 17 {\displaystyle {\sqrt {17}}} when illustrating adjacent right triangles whose bases are units and heights are successive square roots , starting with 1 {\displaystyle 1} . In part due to Theodorus’s work as outlined in Plato’s Theaetetus , it

75-535: A compact executive car produced by Audi Saab 90 , a compact executive car produced by Saab Sunbeam-Talbot 90 , a compact executive car produced by Sunbeam-Talbot Alfa Romeo 90 , an executive car produced by Alfa Romeo Tatra 90 , a prototype mid-size car Rover 90 , a saloon produced by the Rover Company See also [ edit ] All pages with titles containing 90 List of highways numbered 90 [REDACTED] Topics referred to by

100-481: Is centered octagonal ). 90 is equal to the fifth sum of non-triangular numbers, respectively between the fifth and sixth triangular numbers, 15 and 21 (equivalently 16 + 17 ... + 20 ). It is also twice 45 , which is the ninth triangular number, and the second-smallest sum of twelve non-zero integers, from two through thirteen { 2 , 3 , . . . , 13 } {\displaystyle \{2,3,...,13\}} . 90 can be expressed as

125-467: Is 90 (and equivalently, the number of 12-dimensional polyominoes that are prime ). 17 (number) 17 ( seventeen ) is the natural number following 16 and preceding 18 . It is a prime number . 17 was described at MIT as "the least random number", according to the Jargon File . This is supposedly because, in a study where respondents were asked to choose a random number from 1 to 20, 17

150-411: Is a zonohedron with a total of 90 rhombic faces : 60 broad rhombi akin to those in the rhombic dodecahedron with diagonals in 1 : 2 {\displaystyle 1:{\sqrt {2}}} ratio, and another 30 slim rhombi with diagonals in 1 : φ 2 {\displaystyle 1:\varphi ^{2}} golden ratio . The obtuse angle of the broad rhombic faces

175-448: Is also the dihedral angle of a regular icosahedron , with the obtuse angle in the faces of golden rhombi equal to the dihedral angle of a regular octahedron and the tetrahedral vertex-center-vertex angle, which is also the angle between Plateau borders : 109.471 {\displaystyle 109.471} °. It is the dual polyhedron to the rectified truncated icosahedron , a near-miss Johnson solid . On the other hand,

200-402: Is also the sixteenth Perrin number from a sum of 39 and 51 , whose difference is 12 . The members of the first prime sextuplet ( 7 , 11 , 13 , 17, 19 , 23 ) generate a sum equal to 90, and the difference between respective members of the first and second prime sextuplets is also 90, where the second prime sextuplet is ( 97 , 101 , 103 , 107 , 109 , 113 ). The last member of

225-408: Is believed that Theodorus had proved all the square roots of non- square integers from 3 to 17 are irrational by means of this spiral. In three-dimensional space, there are seventeen distinct fully supported stellations generated by an icosahedron . The seventeenth prime number is 59 , which is equal to the total number of stellations of the icosahedron by Miller's rules . Without counting

250-456: Is equal to the sum of a subset of its divisors, it is also the twenty-first semiperfect number . An angle measuring 90 degrees is called a right angle . In normal space , the interior angles of a rectangle measure 90  degrees each, while in a right triangle , the angle opposing the hypotenuse measures 90 degrees, with the other two angles adding up to 90 for a total of 180  degrees. The rhombic enneacontahedron

275-411: Is the product of 9 and 10 , and along with 12 and 56 , one of only a few pronic numbers whose digits in decimal are also successive. 90 is divisible by the sum of its base-ten digits, which makes it the thirty-second Harshad number . The twelfth triangular number 78 is the only number to have an aliquot sum equal to 90, aside from the square of the twenty-fourth prime, 89 (which

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300-440: Is the ninetieth indexed composite number , where the sum of integers { 2 , 3 , . . . , 11 } {\displaystyle \{2,3,...,11\}} is 65 , which in-turn represents the composite index of 90. In the fractional part of the decimal expansion of the reciprocal of 11 in base-10 , " 90 {\displaystyle 90} " repeats periodically (when leading zeroes are moved to

325-705: The 24-cell , itself the simplest parallelotope that is not a zonotope. Seventeen is the highest dimension for paracompact Vineberg polytopes with rank n + 2 {\displaystyle n+2} mirror facets , with the lowest belonging to the third. 17 is a supersingular prime , because it divides the order of the Monster group . If the Tits group is included as a non-strict group of Lie type , then there are seventeen total classes of Lie groups that are simultaneously finite and simple (see classification of finite simple groups ). In base ten , (17, 71) form

350-546: The final stellation of the icosahedron has 90 edges. It also has 92 vertices like the rhombic enneacontahedron, when interpreted as a simple polyhedron . Meanwhile, the truncated dodecahedron and truncated icosahedron both have 90 edges . A further four uniform star polyhedra ( U 37 , U 55 , U 58 , U 66 ) and four uniform compound polyhedra ( UC 32 , UC 34 , UC 36 , UC 55 ) contain 90 edges or vertices . The self-dual Witting polytope contains ninety van Oss polytopes such that sections by

375-451: The English language, the numbers 90 and 19 are often confused, as they sound very similar. When carefully enunciated, they differ in which syllable is stressed: 19 /naɪnˈtiːn/ vs 90 /ˈnaɪnti/. However, in dates such as 1999, and when contrasting numbers in the teens and when counting, such as 17, 18, 19, the stress shifts to the first syllable: 19 /ˈnaɪntiːn/. Ninety is a pronic number as it

400-637: The Witting polytope in four-dimensional complex space . By Coxeter , the incidence matrix configuration of the Witting polytope can be represented as: This Witting configuration when reflected under the finite space PG ⁡ ( 3 , 2 2 ) {\displaystyle \operatorname {PG} {(3,2^{2})}} splits into 85 = 45 + 40 {\displaystyle 85=45+40} points and planes, alongside 27 + 90 + 240 = 357 {\displaystyle 27+90+240=357} lines. Whereas

425-449: The common plane of two non-orthogonal hyperplanes of symmetry passing through the center yield complex 3 { 4 } 3 {\displaystyle _{3}\{4\}_{3}} Möbius–Kantor polygons . The root vectors of simple Lie group E 8 are represented by the vertex arrangement of the 4 21 {\displaystyle 4_{21}} polytope , which shares 240 vertices with

450-444: The end). The eighteenth Stirling number of the second kind S ( n , k ) {\displaystyle S(n,k)} is 90, from a n {\displaystyle n} of 6 {\displaystyle 6} and a k {\displaystyle k} of 3 {\displaystyle 3} , as the number of ways of dividing a set of six objects into three non-empty subsets . 90

475-420: The icosahedron as a zeroth stellation, this total becomes 58 , a count equal to the sum of the first seven prime numbers (2 + 3 + 5 + 7 ... + 17). Seventeen distinct fully supported stellations are also produced by truncated cube and truncated octahedron . Seventeen is also the number of four-dimensional parallelotopes that are zonotopes . Another 34, or twice 17, are Minkowski sums of zonotopes with

500-426: The rhombic enneacontahedron is the zonohedrification of the regular dodecahedron, a honeycomb of Witting polytopes holds vertices isomorphic to the E 8 {\displaystyle \mathrm {E} _{8}} lattice , whose symmetries can be traced back to the regular icosahedron via the icosian ring . The maximal number of pieces that can be obtained by cutting an annulus with twelve cuts

525-517: The same term This disambiguation page lists articles associated with the same number. If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=90&oldid=1253656019 " Category : Lists of ambiguous numbers Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages 90 (number) In

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550-438: The second prime sextuplet, 113, is the 30th prime number . Since prime sextuplets are formed from prime members of lower order prime k -tuples , 90 is also a record maximal gap between various smaller pairs of prime k -tuples (which include quintuplets , quadruplets , and triplets ). 90 is the third unitary perfect number (after 6 and 60 ), since it is the sum of its unitary divisors excluding itself, and because it

575-561: The seventh permutation class of permutable primes . Seventeen is the number of elementary particles with unique names in the Standard Model of physics. Group 17 of the periodic table is called the halogens . The atomic number of chlorine is 17. Some species of cicadas have a life cycle of 17 years (i.e. they are buried in the ground for 17 years between every mating season). Seventeen is: Where Pythagoreans saw 17 in between 16 from its Epogdoon of 18 in distaste,

600-913: The sum of distinct non-zero squares in six ways, more than any smaller number (see image): ( 9 2 + 3 2 ) , ( 8 2 + 5 2 + 1 2 ) , ( 7 2 + 5 2 + 4 2 ) , ( 8 2 + 4 2 + 3 2 + 1 2 ) , ( 7 2 + 6 2 + 2 2 + 1 2 ) , ( 6 2 + 5 2 + 4 2 + 3 2 + 2 2 ) . {\displaystyle (9^{2}+3^{2}),(8^{2}+5^{2}+1^{2}),(7^{2}+5^{2}+4^{2}),(8^{2}+4^{2}+3^{2}+1^{2}),(7^{2}+6^{2}+2^{2}+1^{2}),(6^{2}+5^{2}+4^{2}+3^{2}+2^{2}).} The square of eleven 11 2 = 121 {\displaystyle 11^{2}=121}

625-462: Was the most common choice. This study has been repeated a number of times. 17 is a Leyland number and Leyland prime , using 2 & 3 (2 + 3 ) and using 4 and 5 , Since seventeen is a Fermat prime, regular heptadecagons can be constructed with a compass and unmarked ruler. This was proven by Carl Friedrich Gauss and ultimately led him to choose mathematics over philology for his studies. The minimum possible number of givens for

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