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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 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:

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.

65=1⁵+2⁴+3³+4²+5¹

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 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. 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", 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.
• 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."
• The number of the French department Hautes-Pyrénées

In sports

• NCAA Men's basketball tournament includes 65 college teams
• NFL Houston Oilers Elvin Bethea wore uniform #65
• MotoGP rider Loris Capirossi races with #65

Historical years

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