Number

161

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

Arithmetic Number Cullen Number Deficient Number Flippable Odious Number Palindrome Pernicious Number Recamán's Sequence Semiprime Squarefree Year

Historical context — 161 AD

Calendar year

Year 161 (CLXI) was a common year starting on Wednesday of the Julian calendar.

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Historical context — 161 BC

Calendar year

The Year 161 BC was a year of the pre-Julian Roman calendar.

Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 · English fallback 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, 161
Ended on: Thursday
December 31, 161
Friday the 13ths: 3
3 Friday the 13ths this year.
Decade: 160s
160–169
Century: 2nd century
101–200
Millennium: 1st millennium
1–1000
Years ago: 1,865
1865 years before 2026.

In other calendars

Hebrew: 3921 / 3922 AM
Rosh Hashanah falls in September/October.
Chinese: Year of the zodiac:Metal zodiac:Ox
Sexagenary cycle position 38 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 704 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Ethiopian: 153 / 154 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 83 / 82 Saka
Indian national calendar; year starts in March.

Properties

Parity: Odd
Digit count: 3
Digit sum: 8
Digit product: 6
Digital root: 8
Palindrome: Yes
Bit width: 8 bits
Flips to (rotate 180°): 191
Recamán's sequence: a(94) = 161
Square (n²): 25,921
Cube (n³): 4,173,281
Divisor count: 4
σ(n) — sum of divisors: 192
φ(n) — Euler's totient: 132
Sum of prime factors: 30

Primality

Prime factorization: 7 × 23

Nearest primes: 157 (−4) · 163 (+2)

Divisors & multiples

All divisors (4)

1 · 7 · 23 · 161

Aliquot sum (sum of proper divisors): 31

Factor pairs (a × b = 161)

1 × 161

7 × 23

First multiples

161 · 322 (double) · 483 · 644 · 805 · 966 · 1,127 · 1,288 · 1,449 · 1,610

Sums & aliquot sequence

As consecutive integers: 80 + 81 20 + 21 + … + 26 5 + 6 + … + 18

Aliquot sequence: 161 → 31 → 1 → 0 — terminates at zero

Representations

In words: one hundred sixty-one
Ordinal: 161st
Roman numeral: CLXI
Binary: 10100001
Octal: 241
Hexadecimal: 0xA1
Base64: oQ==
One's complement: 94 (8-bit)

In other bases

ternary (3) 12222

quaternary (4) 2201

quinary (5) 1121

senary (6) 425

septenary (7) 320

nonary (9) 188

undecimal (11) 137

duodecimal (12) 115

tridecimal (13) c5

tetradecimal (14) b7

pentadecimal (15) ab

Historical numeral systems

Babylonian (base 60): 𒁹𒁹 𒌋𒌋𒌋𒌋𒁹
Egyptian hieroglyphic: 𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓏺
Greek (Milesian): ρξαʹ
Mayan (base 20): 𝋨·𝋡
Chinese: 一百六十一
Chinese (financial): 壹佰陸拾壹

In other modern scripts

Eastern Arabic ١٦١ Devanagari १६१ Bengali ১৬১ Tamil ௧௬௧ Thai ๑๖๑ Tibetan ༡༦༡ Khmer ១៦១ Lao ໑໖໑ Burmese ၁၆၁

Digit at this position in famous constants

π — Pi (π): Digit 161 = 2
e — Euler's number (e): Digit 161 = 1
φ — Golden ratio (φ): Digit 161 = 3
√2 — Pythagoras's (√2): Digit 161 = 2
ln 2 — Natural log of 2: Digit 161 = 7
γ — Euler-Mascheroni (γ): Digit 161 = 5

Also seen as

Unicode codepoint

Inverted Exclamation Mark

U+00A1

Other punctuation (Po)

UTF-8 encoding: C2 A1 (2 bytes).

Lookup U+00A1 on Compart ↗ Lookup on FileFormat.Info ↗

Network port

TCP/UDP port 161 is the well-known port for SNMP — Simple Network Management Protocol.

Hex color

#0000A1

RGB(0, 0, 161)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.0.161.

Address: 0.0.0.161
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.0.161

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