Number

291

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

291 (two hundred ninety-one) is an odd 3-digit number. It is a composite number with 4 divisors, and factors as 3 × 97. Written other ways, in Roman numerals it is CCXCI and in binary, 100100011.

Arithmetic Number Cube-Free Deficient Number Evil Number Happy Number Recamán's Sequence Semiprime Squarefree Year

Interestingness

★ ★ ★ ★ ☆

6 notable facts · grade B

279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303

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Historical context — 291 AD

Calendar year

Year 291 (CCXCI) was a common year starting on Thursday of the Julian calendar.

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

Historical context — 291 BC

Calendar year

Year 291 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, 291
Ended on: Thursday
December 31, 291
Friday the 13ths: 3
3 Friday the 13ths this year.
Decade: 290s
290–299
Century: 3rd century
201–300
Millennium: 1st millennium
1–1000
Years ago: 1,735
1735 years before 2026.

In other calendars

Hebrew: 4051 / 4052 AM
Rosh Hashanah falls in September/October.
Chinese: Year of the zodiac:Metal zodiac:Pig
Sexagenary cycle position 48 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 834 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Ethiopian: 283 / 284 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 213 / 212 Saka
Indian national calendar; year starts in March.

Properties

Parity: Odd
Digit count: 3
Digit sum: 12
Digit product: 18
Digital root: 3
Palindrome: No
Bit width: 9 bits
Reversed: 192
Recamán's sequence: a(666) = 291
Square (n²): 84,681
Cube (n³): 24,642,171
Divisor count: 4
σ(n) — sum of divisors: 392
φ(n) — Euler's totient: 192
Sum of prime factors: 100

Primality

Prime factorization: 3 × 97

Nearest primes: 283 (−8) · 293 (+2)

Divisors & multiples

All divisors (4)

1 · 3 · 97 · 291

Aliquot sum (sum of proper divisors): 101

Factor pairs (a × b = 291)

1 × 291

3 × 97

First multiples

291 · 582 (double) · 873 · 1,164 · 1,455 · 1,746 · 2,037 · 2,328 · 2,619 · 2,910

Sums & aliquot sequence

As consecutive integers: 145 + 146 96 + 97 + 98 46 + 47 + 48 + 49 + 50 + 51

Aliquot sequence: 291 → 101 → 1 → 0 — terminates at zero

Continued fraction of √n

√291 = [17; (17, 34)]

Period length 2 — the block in parentheses repeats forever.

Representations

In words: two hundred ninety-one
Ordinal: 291st
Roman numeral: CCXCI
Binary: 100100011
Octal: 443
Hexadecimal: 0x123
Base64: ASM=
One's complement: 65,244 (16-bit)
Scientific notation: 2.91 × 10²
As a duration: 291 s = 4 minutes, 51 seconds

In other bases

ternary (3) 101210

quaternary (4) 10203

quinary (5) 2131

senary (6) 1203

septenary (7) 564

nonary (9) 353

undecimal (11) 245

duodecimal (12) 203

tridecimal (13) 195

tetradecimal (14) 16b

pentadecimal (15) 146

Palindromic in base 9

As an angle

291°

291° ≈ 5.079 rad

Compass bearing: WNW (west-northwest)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒁹𒁹𒁹𒁹 𒌋𒌋𒌋𒌋𒌋𒁹
Egyptian hieroglyphic: 𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓏺
Greek (Milesian): σϟαʹ
Mayan (base 20): 𝋮·𝋫
Chinese: 二百九十一
Chinese (financial): 貳佰玖拾壹

In other modern scripts

Eastern Arabic ٢٩١ Devanagari २९१ Bengali ২৯১ Tamil ௨௯௧ Thai ๒๙๑ Tibetan ༢༩༡ Khmer ២៩១ Lao ໒໙໑ Burmese ၂၉၁

Digit at this position in famous constants

π — Pi (π): Digit 291 = 6
e — Euler's number (e): Digit 291 = 7
φ — Golden ratio (φ): Digit 291 = 4
√2 — Pythagoras's (√2): Digit 291 = 9
ln 2 — Natural log of 2: Digit 291 = 1
γ — Euler-Mascheroni (γ): Digit 291 = 0

Also seen as

Unicode codepoint

Latin Small Letter G With Cedilla

U+0123

Lowercase letter (Ll)

UTF-8 encoding: C4 A3 (2 bytes).

Lookup U+0123 on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#000123

RGB(0, 1, 35)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.1.35.

Address: 0.0.1.35
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.1.35

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

Musical pitch

Heard as a frequency, 291 Hz is closest to:

Concert pitch (A4 = 440 Hz): D4 (293.7 Hz, -16¢)
Scientific pitch (C4 = 256 Hz): D4 (287.4 Hz, +22¢)
Baroque pitch (A4 = 415 Hz): D♯4 (293.4 Hz, -15¢)