Numbers 8100-8199

A page of the Numeropedia - the Special Encyclopedia of Numbers

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8,100

[Math.]  Sum (in degrees) of all internal angles of a 47-side polygon.

8,120

[Library]  ISBN-0-8120 is the International Standard Book Number for books published by Barron’s Educational Series.

8,128

[Math.]  A triangular number (sum of all integers from 1 to 127): 8128 = 1+2+…+126+127.

[Math.]  The 4th perfect number; i.e., a number equal to the sum of all of its proper divisors, including 1 (or also called aliquot divisors).  The first perfect numbers are: 6, 28, 496, 8128, 212(213–1) = 33550336, 216(217–1) = 8,589,869,056 and 218(219–1) = 137,438,691,328…

8,135

[Library]  ISBN-0-8135 is the International Standard Book Number for books published by Rivergate Books/ Rutgers University Press.

8,149

[Math.]  Two multiples of number 8149, 8149×2 = 16,298 and 8149×7 = 57,043, use each of 10 digits 0-9 once.

8,169

[Math.]  The equality 8169×3 = 24,507 uses each of 10 digits 0-9 once.

[Math.]  The number of pairs of twin prime numbers less than 1,000,000.

8,171

[Math.]  A sequence of prime numbers of similar pattern: 11171, 10181, 9181, 8171, 7151, 6121 and 5081, whose differences are 990, 1000, 1010, 1020, 1030 and 1040, respectively.

8,174

[Math.]  The ratio 65392/8174 = 8, using each of 9 digits 1-9 once, shows how to arrange a 9-book set on 2 shelves to mark the book #8.

8,176

[Library]  ISBN-0-8176 is the International Standard Book Number for books published by Birkhäuser.

8,179

[Math.]  A prime number.

[Math.]  The ratio 65432/8179 = 8, using each of 9 digits 1-9 once, shows how to arrange a 9-book set on 2 shelves to mark the book #8.

[Math.]  Two multiples of number 8179, 8179×4 = 32,716 and 8179×5 = 40,895, use each of 10 digits 0-9 once.

8,191

[Math.]  The 5th Mersenne prime number: 213–1.

[Math.]  A prime number, concatenated by powers of 9: 81 = 92, 9 and 1; also sum of powers of 90: 8191 = 1+90+902.

8,192

[Math.]  8192 = 23×45.