This article may contain indiscriminate, excessive, or irrelevant examples. (March 2010) |

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Cardinal | sixty-five | |||

Ordinal | 65th (sixty-fifth) | |||

Factorization | 5 × 13 | |||

Divisors | 1, 5, 13, 65 | |||

Greek numeral | ΞΕ´ | |||

Roman numeral | LXV | |||

Binary | 1000001_{2} | |||

Ternary | 2102_{3} | |||

Quaternary | 1001_{4} | |||

Quinary | 230_{5} | |||

Senary | 145_{6} | |||

Octal | 101_{8} | |||

Duodecimal | 55_{12} | |||

Hexadecimal | 41_{16} | |||

Vigesimal | 35_{20} | |||

Base 36 | 1T_{36} |

**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.^{[2]} It is also a Cullen number.^{[3]} Given 65, the Mertens function returns 0.^{[4]}

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.^{[5]}

65 is the smallest integer that can be expressed as a sum of two distinct positive squares in two ways, 65 = 8^{2} + 1^{2} = 7^{2} + 4^{2}.

It appears in the Padovan sequence, preceded by the terms 28, 37, 49 (it is the sum of the first two of these).^{[6]}

There are only 65 known Euler's idoneal numbers.

65 = 1^{5} + 2^{4} + 3^{3} + 4^{2} + 5^{1}.

65 is the length of the hypotenuse of 4 different Pythagorean triangles, the lowest number to have more than 2: 65^{2} = 16^{2} + 63^{2} = 33^{2} + 56^{2} = 39^{2} + 52^{2} = 25^{2} + 60^{2}. 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 galaxy of magnitude 10.5 in the constellation Leo
- The New General Catalogue object NGC 65, a spiral galaxy in the constellation Cetus

## 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"
- Odd Future group MellowHype has performed a song entitled "65"

## In other fields

- 65 miles per hour is a common speed limit on expressways in many U.S. states, primarily in the eastern and central United States. (In the western United States, a common speed limit is 70 m.p.h., and in some places it is 75 m.p.h.).
- +65 is the code for international direct dial telephone calls to Singapore.
- as an age, 65 years old is
- the traditional age for retirement in the United Kingdom, Germany, the United States, Canada, and several other countries.
- in the U.S., the age at which a person is eligible to obtain Medicare.

- CVN-65 is the designation of the U.S. Navy's first nuclear-powered aircraft carrier, the USS Enterprise (CVN-65).
- 65 is the minimum grade or average required to pass an exam, or a class, in some schools.
- The setting of the American classic TV series
*Naked City*(1958–63) was the 65th Precinct in New York City (sometimes referred to as simply "the 65"). - 65 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.
- The M-65 field jacket was commonly worn by American troops during the War in Vietnam.
- A 65th anniversary is sometimes referred to as a sapphire jubilee.
- The AGM-65 Maverick is a mass-produced air-to-ground tactical missile (AGM) designed for close air support against a wide range of targets.

## References

**^**Sloane, N. J. A. (ed.). "Sequence A001358".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation.**^**"Sloane's A000567 : Octagonal numbers".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-30.**^**"Sloane's A002064 : Cullen numbers".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-30.**^**"Sloane's A028442 : Numbers n such that Mertens' function is zero".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-30.**^**Sloane, N. J. A. (ed.). "Sequence A006003".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation.**^**"Sloane's A000931 : Padovan sequence".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-30.