660

[Measure]  The number of feet in a furlong.

U.S. customary units for linear measures: 1 mile = 8 furlongs = 320 rods = 1,760 yards = 5,280 feet = 63,360 inches.

 

[World]  The ISO country code for Anguilla. (ISO-3166)

 

661

[Math.]  A prime number.

 

662

[World]  The ISO country code for St. Lucia. (ISO-3166)

 

663

[Tech.]  The approximate speed of Mach 2, (meters/second).

 

664

[Phone]  The telephone area code for Montserrat (within U.S./NANPA).

  

665

[Math.]  Repeatedly inserting numbers 42 between the digits 4 and 2 in the square number 4225 = 652 yields other squares 442225 = 6652, 44422225 = 66652, 4444222225 = 666652, 444442222225 = 6666652

 

[Math.]  Square of numbers of similar pattern xxy, where y = x–1.

* 1102 = 012,100 & 012+100 = 112 = 110+2.

* 3322 = 110,224 & 110+224 = 334 = 332+2.

Similarly, 3…322 = 1…102…24 & 1…10+2…24 = 3…34 = 3…32+2.

* 4432 = 196,249 & 196+249 = 445 = 443+2

* 6652 = 442,225 & 442+225 = 667 = 665+2.

Similarly, 6…652 = 4…422…25 & 4…42+2…25 = 6…67 = 6…65+2.

* 7762 = 602,176 & 602+176 = 778 = 776+2.

 

666

[Chemistry]  Name of a popular chemical compound: Hexachlorocyclohexane C6H6Cl6 (or Benzene Hexachloride).

 

[Language]  Its Roman numeral representation (DCLXVI) uses once each the Roman numeral symbols with values under 1,000, occurring in exact reverse order of their respective values (D = 500, C = 100, L = 50, X = 10, V = 5, I = 1).

 

[Math.]  A triangular number (sum of all integers from 1 to 36): 666 = 1+2+…+35+36.

The only triangular numbers whose digits are repeated are: 55, 66 and 666.

 

[Math.]  666 = 22+32+52+72+112+132+172, sum of squares of the first 7 primes.

 

[Math.]  666 = 13+23+33+43+53+63+53+43+33+23+13 = 63+63+63+6+6+6.

 

[Math.]  6666 = 87,266,061,345,623,616 has 6 digits 6.

 

[Math.]  The number of digits of an apocalypse number. E.g., the Fibonacci number F3184 is an apocalypse number.

 

[Math.]  An apocalyptic number is a number of the form 2n that contains the digits 666: e.g., 2157, 2192, 2218, 2220, 2222, 2224, 2226, 2243, 2245, 2247, 2251,…, 2666

A double apocalyptic number is a number of the form 2n that contains the digits 666,666.

 

[Math.]  A Smith number: 666 = 2×3×3×37 where 2+3+3+3+7 = 6+6+6 = 18. Smith number is a composite number whose sum of its digits is equal to the sum of digits of all of its prime factors.

 

[Phone]  The number to key in text messaging on telephone keypad for letter O.

 

[Theology]  The Holy Bible, Revelation 13:18: “…Whoever is intelligent can work out the meaning of the number of the beast, because the number stands for a man’s name. Its number is 666”.

 

[World]  The ISO country code for St. Pierre and Miquelon. (ISO-3166).

 

666.3332...

[Math.]

401/2 = 6.32…

44001/2 = 66.332…

4440001/2 = 666.3332…

444400001/2 = 6666.33332…

44444000001/2 = 66666.333332…

4444440000001/2 = 666666.3333332…

 

667

[Math.]  333,667,000 = 3333+6673+0003.

334,000,667 = 3343+0003+6673.

 333,667,001 = 3333+6673+0013.

 

[Math.]  1,334,667 = 13342–6672 = (1334+667)×667, where 1334 = 667×2.

 

[Math.]  Repeatedly inserting numbers 48 in the middle of the square number 49 yields other squares 4489 = 672, 444889 = 6672, 44448889 = 66672

 

[Math.]  Numbers of the same pattern, xxy, where y = x +1: 1122 = 012,544 & 012+544 = 556 & 5562 = 309,136 & 309+136 = 445 & 4452 = 198,025 & 198+025 = 223 & 2232 = 049,729 & 049+729 = 778 & 7782 = 605,284 & 605+284 = 889 & 8892 = 790,321 & 790+321 = 1111. Also: 3342 = 111556 & 111+556 = 667.

 

668

[Math.]  334,668 = 6682–3342 = (334+668)×334, where 668 = 334×2.

 

669 

[Library] ISBN-0-669 is the International Standard Book Number for books published by D. C. Heath and Company (or Better Homes and Gardens Books).

 

661663, 664, 666, 667, 668 & 669 and  

670, 671, 672, 674 & 675

[Math.]

66×64 = 4224

66×67 = 4422

66×68 = 4488

66×69 = 4554

66×74 = 4884

 

666×661 = 440,226

666×666 = 443,556

666×669 = 445,554

666×672 = 447,552

666×663 = 441,558

666×667 = 444,222

666×670 = 446,220

666×674 = 448,884

666×664 = 442,224

666×668 = 444,888

666×671 = 446,886

666×675 = 449,550

… (generalizable pattern) …

 

660-669

[Library]  Numbers 600-699 are the first 3 digits in Dewey Decimal Classification System call numbers for library books in Applied Sciences and Technology (Medicine, Agriculture and Engineering…). Numbers 660-669 are for books in Chemical Engineering.