65 (number)

From Wikipedia, the free encyclopedia

"LXV" redirects here. For the IATA/FAA code, see Lake County Airport (Colorado).

65 (sixty-five) is the natural number following 64 and preceding 66.

← 60 61 62 63 64 65 66 67 68 69 → List of numbers — Integers 0 10 20 30 40 50 60 70 80 90 →
Cardinal	65 sixty-five
Ordinal	65th sixty-fifth
Factorization	$5 \cdot 13$
Divisors	1, 5, 13, 65
Roman numeral	LXV
Binary	1000001
Hexadecimal	41

1 In mathematics
2 In science
- 2.1 Astronomy
3 In other fields
4 In sports
5 Historical years

[edit] In mathematics

Sixty-five is the 19th semiprime and the 3rd of the form (5.q)it is an octagonal number. It is also a Cullen number. Given 65, the Mertens function returns 0.

Sixty-five has an aliquot sum of 19 and is the first composite number in the 19-aliquot tree.

This number is the magic constant of 5 by 5 normal magic square:

$\begin{bmatrix} 17 & 24 & 1 & 8 & 15 \\ 23 & 5 & 7 & 14 & 16 \\ 4 & 6 & 13 & 20 & 22 \\ 10 & 12 & 19 & 21 & 3 \\ 11 & 18 & 25 & 2 & 9 \end{bmatrix}.$

This number is also the magic constant of n-Queens Problem for n = 5.

65 is the smallest integer that can be expressed as a sum of two distinct positive squares in two ways, 65 = 8² + 1² = 7² + 4².

It appears in the Padovan sequence, preceded by the terms 28, 37, 49 (it is the sum of the first two of these).

There are only 65 known Euler's idoneal numbers.

[edit] In science

The atomic number of terbium, a lanthanide

[edit] Astronomy

Messier object M65, a magnitude 10.5 galaxy in the constellation Leo

The New General Catalogue object NGC 65, a spiral galaxy in the constellation Cetus

The Saros number of the solar eclipse series which began on -749 April 24 and ended on 513 May 20. The duration of Saros series 65 was 1262.1 years, and it contained 71 solar eclipses.

The Saros number of the lunar eclipse series which began on -736 August 11 and ended on 797 February 16. The duration of Saros series 65 was 1532.5 years, and it contained 86 lunar eclipses.

[edit] In other fields

Sixty-five is:

A common speed limit, in miles per hour, for freeways in many U.S. states, primarily in the eastern United States (in the western United States, the common limit is 70 and in some places 75)
The designation of Interstate 65, a freeway that runs from Alabama to Indiana
The code for international direct dial phone calls to Singapore
The traditional age for retirement in the United Kingdom, Germany and other countries. It was previously the age at which a person in the United States could retire with full Social Security benefits; however, recent changes in the law have increased this age for younger workers due to improvements in life expectancy
The registry of the U.S. Navy's nuclear aircraft carrier USS Enterprise (CVN-65)
65 is the minimum grade required to pass an exam, or class, in many areas
Paul Davis had a hit song "65 Love Affair" in 1982
Sammy Hagar re-recorded his hit "I Can't Drive 55" in 2001 for NBC's NASCAR broadcasts to reflect higher speed limits. The song was used from 2001 until 2004 to introduce Budweiser Pole Award winners on NBC and TNT broadcasts.
65 is a commonly used abbreviation for the Sheffield, UK, post-rock band 65daysofstatic.
The setting of Naked City (1958 - 63) was New York's 65th Precinct
Referenced in "Heroes and Villains" by the Beach Boys: "At threescore and five / I'm very much alive / I've still got the jive / to survive with the Heroes and Villains."