Number

2,161

2,161 is a prime, odd.

2,161 (two thousand one hundred sixty-one) is an odd 4-digit number. It is a prime number — divisible only by 1 and itself. Written other ways, in Roman numerals it is MMCLXI and in binary, 100001110001.

Arithmetic Number Cube-Free Deficient Number Odious Number Pernicious Number Prime Pythagorean Prime Recamán's Sequence Squarefree

Interestingness

★ ★ ★ ★ ☆

6 notable facts · grade B

2,149 2,150 2,151 2,152 2,153 2,154 2,155 2,156 2,157 2,158 2,159 2,160 2,161 2,162 2,163 2,164 2,165 2,166 2,167 2,168 2,169 2,170 2,171 2,172 2,173

less more

Properties

Parity: Odd
Digit count: 4
Digit sum: 10
Digit product: 12
Digital root: 1
Palindrome: No
Bit width: 12 bits
Reversed: 1,612
Recamán's sequence: a(3,429) = 2,161
Square (n²): 4,669,921
Cube (n³): 10,091,699,281
Divisor count: 2
σ(n) — sum of divisors: 2,162
φ(n) — Euler's totient: 2,160

Primality

2,161 is prime. It has exactly two divisors: 1 and itself.

Divisors & multiples

All divisors (2)

1 · 2161

Aliquot sum (sum of proper divisors): 1

Factor pairs (a × b = 2,161)

1 × 2161

First multiples

2,161 · 4,322 (double) · 6,483 · 8,644 · 10,805 · 12,966 · 15,127 · 17,288 · 19,449 · 21,610

Sums & aliquot sequence

As a sum of two squares: 15² + 44²

As consecutive integers: 1,080 + 1,081

Continued fraction of √n

√2,161 = [46; (2, 18, 10, 3, 1, 1, 1, 1, 1, 2, 5, 11, 2, 3, 2, 1, 1, 7, 1, 6, 3, 1, 2, 1, …)]

Representations

In words: two thousand one hundred sixty-one
Ordinal: 2161st
Roman numeral: MMCLXI
Binary: 100001110001
Octal: 4161
Hexadecimal: 0x871
Base64: CHE=
One's complement: 63,374 (16-bit)
Scientific notation: 2.161 × 10³
As a duration: 2,161 s = 36 minutes, 1 second

In other bases

ternary (3) 2222001

quaternary (4) 201301

quinary (5) 32121

senary (6) 14001

septenary (7) 6205

nonary (9) 2861

undecimal (11) 1695

duodecimal (12) 1301

tridecimal (13) ca3

tetradecimal (14) b05

pentadecimal (15) 991

As an angle

2,161° = 6 × 360° + 1°

1° ≈ 0.017 rad

Compass bearing: N (north)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒌋𒌋𒌋𒁹𒁹𒁹𒁹𒁹𒁹 𒁹
Egyptian hieroglyphic: 𓆼𓆼𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓏺
Greek (Milesian): ͵βρξαʹ
Mayan (base 20): 𝋥·𝋨·𝋡
Chinese: 二千一百六十一
Chinese (financial): 貳仟壹佰陸拾壹

In other modern scripts

Eastern Arabic ٢١٦١ Devanagari २१६१ Bengali ২১৬১ Tamil ௨௧௬௧ Thai ๒๑๖๑ Tibetan ༢༡༦༡ Khmer ២១៦១ Lao ໒໑໖໑ Burmese ၂၁၆၁

Digit at this position in famous constants

π — Pi (π): Digit 2,161 = 7
e — Euler's number (e): Digit 2,161 = 4
φ — Golden ratio (φ): Digit 2,161 = 8
√2 — Pythagoras's (√2): Digit 2,161 = 0
ln 2 — Natural log of 2: Digit 2,161 = 4
γ — Euler-Mascheroni (γ): Digit 2,161 = 6

Also seen as

Prime neighborhood

Adjacent primes:

Previous prime: 2,153 (gap of 8)
Next prime: 2,179 (gap of 18)

Unicode codepoint

ࡱ

Arabic Letter Alef With Attached Top Right Fatha

U+0871

Other letter (Lo)

UTF-8 encoding: E0 A1 B1 (3 bytes).

Lookup U+0871 on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#000871

RGB(0, 8, 113)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.8.113.

Address: 0.0.8.113
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.8.113

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

Musical pitch

Heard as a frequency, 2,161 Hz is closest to:

Concert pitch (A4 = 440 Hz): C♯7 (2217.5 Hz, -45¢ — about midway to C7)
Scientific pitch (C4 = 256 Hz): C♯7 (2169.8 Hz, -7¢)
Baroque pitch (A4 = 415 Hz): D7 (2215.8 Hz, -43¢)

Position in π

The digit sequence 2161 first appears in π at position 6,796 of the decimal expansion (the 6,796ordinal-suffix:th digit after the integer 3).

Search range: the first 1,000,000 fractional digits of π. Any 6-digit-or-shorter string is virtually guaranteed to appear in there — the more interesting signal is the position.

Look up 2161 on Pi Search ↗