65

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← 64 66 → 65
← 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	sixty-five
Ordinal	65th (sixty-fifth)
Factorization
Divisors	1, 5, 13, 65
Roman numeral	LXV
Binary	10000012
Octal	1018
Duodecimal	5512
Hexadecimal	4116

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

In mathematics

Sixty-five is the 23rd^[1] 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:

This number is also the magic constant of n-Queens Problem for n = 5.^[2]

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.

65=1⁵+2⁴+3³+4²+5¹

65 is the length of the hypotenuse of 4 different pythagorean triangles, the lowest number to have more than 2: 65² = 16² + 63² = 33² + 56² = 39² + 52² = 25² + 60². The first two are "primitive", and 65 is the lowest number to be the largest side of more than one such triple.

In science

• The atomic number of terbium, a lanthanide

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. 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. The duration of Saros series 65 was 1532.5 years, and it contained 86 lunar eclipses.

In music

• "65 Love Affair", singer Paul Davis' hit song in 1982
• Sammy Hagar re-recorded his hit "I Can't Drive 55", with the 55 changed to 65, 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
• Referenced in "Heroes and Villains" by the Beach Boys: "At 60 and 5 / I'm very much alive / I've still got the jive / to survive with the Heroes and Villains"

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
• Municipal Okrug 65, a municipal okrug of Primorsky District of Saint Petersburg, Russia
• +65 is the code for international direct dial phone calls to Singapore
• The traditional age for retirement in the United Kingdom, Germany and other countries.
• 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
• The setting of Naked City (1958 - 63) was New York's 65th Precinct
• The number of the French department Hautes-Pyrénées
• 65 is commonly used in names of many dishes of South India cuisine, for instance Chicken 65

In sports

• MotoGP rider Loris Capirossi races with #65

Historical years

65 A.D., 65 B.C., 1965, 2065, etc.

References

1. ^ (sequence A001358 in OEIS)
2. ^ Sloane's A006003 . The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.