Numbers 720-729

A page of the Numeropedia - the Special Encyclopedia of Numbers

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720

[Calendar]  The number of hours in a 30-day month.

[Math.]  6 factorial = 6! = 1×2×3×4×5×6 = 720.

[Math.]  Solutions of the factorial equations n! = ab!:

6! = 5!×3! and 10! = 7!×6!.

[Math.]  Sum (in degrees) of all internal angles of a 6-side polygon.

[Measure]  A cable’s length = 120 fathoms = 720 feet.

[Measure]  The time (minutes) that the hour hand rotates one full cycle (revolution) on a mechanical clock or watch.

[Money]  Credit scores by FICO (Fair Isaac Corporation) range from about 300 to 850 and exhibit a left-skewed distribution with a U.S. median around 725. A score above 720 is considered “good credit” and below 600 is “poor credit”.

721

722

[Math.]  The sum s(n) = 2^(2n)+3^(2n)+5^(2n) is always divisible by 19 and the sum t(n) = 2^(4n)+3^(4n)+5^(4n) is always divisible by 192 for any integer n > 0: s(2) = 24+34+54 = 722 = t(1).

723

724

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

725

[Money]  Credit scores by FICO (Fair Isaac Corporation) range from about 300 to 850 and exhibit a left-skewed distribution with a U.S. median around 725. A score above 720 is considered “good credit” and below 600 is “poor credit”.

[Math.]  7252 = 525,625, involved 3 number 525, 625 and 725.

726

[Geology]  The height (feet) of the 1,244-foot-long Hoover Dam on the Colorado River, built in 1931-1936 and cost U.S. \$385 million. It is home to Lake Mead, the U.S. largest reservoir.

727

[Math.]  A palindromic prime number.

[Math.]  A square number 7272 = 528,529, formed by concatenation of 2 consecutive numbers.

[Tech.]  Boeing 727 airplane, a member in the family of passenger airplane/jetliner models “7n7”: 707, 717, 727, 737, 747, 757, 767, 777, 7E7 and 787.

728 & 729

[Math.]  The pair (728, 729) is Smith brothers (consecutive Smith numbers). Smith number is a composite number whose sum of its digits is equal to the sum of digits of all of its prime factors.

729

[Math.]  A cube number that is the sum of 3 cube numbers: 729 = 93 = 13+63+83. The largest 3-digit cube number.

[Math.]  729 = 272 = (1+2+2+2+4+4+4+8)2 =  13+23+23+23+43+43+43+83.

[Tech.]  The “number system” code of an EAN-13 barcode for Israel’s products.

720-729

[Library]  Numbers 700-799 are the first 3 digits in Dewey Decimal Classification System call numbers for library books in Fine Arts (Painting, Music, Sport and Photography…). Numbers 720-729 are for books in Architecture.