Number

65

65 is a composite number, odd, a calendar year.

65 (sixty-five) is an odd 2-digit number. It is a composite number with 4 divisors, and factors as 5 × 13. Written other ways, in Roman numerals it is LXV and in binary, 1000001.

Arithmetic Number Binary Palindrome Cube-Free Cullen Number Deficient Number Evil Number Magic Constant Octagonal Padovan Number Pernicious Number Recamán's Sequence Semiprime Squarefree Year

Interestingness

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10 notable facts · grade A

53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77

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Historical context — 65 AD

Calendar year

AD 65 (LXV) was a common year starting on Tuesday of the Julian calendar.

Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 Read the full article on Wikipedia →

Historical context — 65 BC

Calendar year

The year 65 BC was a year of the pre-Julian Roman calendar.

Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 Read the full article on Wikipedia →

Year facts

Year type: Common year
Standard 365-day year; not divisible by 4 (or divisible by 100 but not 400).
Days in year: 365
ISO weeks: 53
Long year: contains 53 ISO weeks.
Started on: Thursday
January 1, 65
Ended on: Thursday
December 31, 65
Friday the 13ths: 3
3 Friday the 13ths this year.
Decade: 60s
60–69
Century: 1st century
1–100
Millennium: 1st millennium
1–1000
Years ago: 1,961
1961 years before 2026.

In other calendars

Hebrew: 3825 / 3826 AM
Rosh Hashanah falls in September/October.
Chinese: Year of the zodiac:Wood zodiac:Ox
Sexagenary cycle position 2 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 608 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Ethiopian: 57 / 58 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): -13 / -14 Saka
Indian national calendar; year starts in March.

Properties

Parity: Odd
Digit count: 2
Digit sum: 11
Digit product: 30
Digital root: 2
Palindrome: No
Bit width: 7 bits
Reversed: 56
Recamán's sequence: a(97) = 65
Square (n²): 4,225
Cube (n³): 274,625
Divisor count: 4
σ(n) — sum of divisors: 84
φ(n) — Euler's totient: 48
Sum of prime factors: 18

Primality

Prime factorization: 5 × 13

Nearest primes: 61 (−4) · 67 (+2)

Divisors & multiples

All divisors (4)

1 · 5 · 13 · 65

Aliquot sum (sum of proper divisors): 19

Factor pairs (a × b = 65)

1 × 65

5 × 13

First multiples

65 · 130 (double) · 195 · 260 · 325 · 390 · 455 · 520 · 585 · 650

Sums & aliquot sequence

As a sum of two squares: 1² + 8² = 4² + 7²

As a sum of two cubes: 1³ + 4³

As consecutive integers: 32 + 33 11 + 12 + 13 + 14 + 15 2 + 3 + … + 11

Aliquot sequence: 65 → 19 → 1 → 0 — terminates at zero

Continued fraction of √n

√65 = [8; (16)]

Period length 1 — the block in parentheses repeats forever.

Representations

In words: sixty-five
Ordinal: 65th
Roman numeral: LXV
Binary: 1000001
Octal: 101
Hexadecimal: 0x41
Base64: QQ==
One's complement: 190 (8-bit)
Scientific notation: 6.5 × 10¹
As a duration: 65 s = 1 minute, 5 seconds

In other bases

ternary (3) 2102

quaternary (4) 1001

quinary (5) 230

senary (6) 145

septenary (7) 122

nonary (9) 72

undecimal (11) 5a

duodecimal (12) 55

tridecimal (13) 50

tetradecimal (14) 49

pentadecimal (15) 45

Palindromic in base 2, base 4, base 8

As an angle

65°

65° ≈ 1.134 rad

Compass bearing: ENE (east-northeast)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒁹 𒁹𒁹𒁹𒁹𒁹
Egyptian hieroglyphic: 𓎆𓎆𓎆𓎆𓎆𓎆𓏺𓏺𓏺𓏺𓏺
Greek (Milesian): ξεʹ
Mayan (base 20): 𝋣·𝋥
Chinese: 六十五
Chinese (financial): 陸拾伍

In other modern scripts

Eastern Arabic ٦٥ Devanagari ६५ Bengali ৬৫ Tamil ௬௫ Thai ๖๕ Tibetan ༦༥ Khmer ៦៥ Lao ໖໕ Burmese ၆၅

Digit at this position in famous constants

π — Pi (π): Digit 65 = 3
e — Euler's number (e): Digit 65 = 7
φ — Golden ratio (φ): Digit 65 = 7
√2 — Pythagoras's (√2): Digit 65 = 9
ln 2 — Natural log of 2: Digit 65 = 4
γ — Euler-Mascheroni (γ): Digit 65 = 8

Also seen as

ASCII character

As an ASCII codepoint, 65 is A. Printable ASCII character A.

Hex color

#000041

RGB(0, 0, 65)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.0.65.

Address: 0.0.0.65
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.0.65

Unspecified address (0.0.0.0/8) — "this network" placeholder.

US numbered highway

Matches numbered highway designation:

I-65 — Mobile, AL to Gary, IN.

Interstate 65 on Wikipedia ↗

Musical pitch

Heard as a frequency, 65 Hz is closest to:

Concert pitch (A4 = 440 Hz): C2 (65.4 Hz, -11¢)
Scientific pitch (C4 = 256 Hz): C2 (64 Hz, +27¢)
Baroque pitch (A4 = 415 Hz): C♯2 (65.4 Hz, -10¢)

(very low — many laptop and phone speakers can't reproduce it)

As a MIDI note number, 65 is F4 (349.2 Hz at concert pitch).

Atomic number

On the periodic table, atomic number 65 is Terbium (Tb) — period 6.

Terbium on Wikipedia ↗