181
181 is a prime, odd, a calendar year.
Historical context — 181 AD
Calendar year
Year 181 (CLXXXI) was a common year starting on Sunday of the Julian calendar.
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Historical context — 181 BC
Calendar year
Year 181 BC was a year of the pre-Julian Roman calendar.
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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
- 52
- Started on
-
Monday
January 1, 181
- Ended on
-
Monday
December 31, 181
- Friday the 13ths
-
2
2 Friday the 13ths this year.
- Decade
-
180s
180–189
- Century
-
2nd century
101–200
- Millennium
-
1st millennium
1–1000
- Years ago
-
1,845
1845 years before 2026.
In other calendars
- Hebrew
-
3941 / 3942 AM
Rosh Hashanah falls in September/October.
- Chinese
-
Year of the zodiac:Metal zodiac:Rooster
Sexagenary cycle position 58 of 60. Lunar new year falls in late January / mid-February.
- Buddhist Era
-
724 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Ethiopian
-
173 / 174 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
103 / 102 Saka
Indian national calendar; year starts in March.
Properties
Primality
181 is prime. It has exactly two divisors: 1 and itself.
Divisors & multiples
Sums & aliquot sequence
Representations
- In words
- one hundred eighty-one
- Ordinal
- 181st
- Roman numeral
- CLXXXI
- Binary
- 10110101
- Octal
- 265
- Hexadecimal
- 0xB5
- Base64
- tQ==
- One's complement
- 74 (8-bit)
Historical numeral systems
- Babylonian (base 60)
- 𒁹𒁹𒁹 𒁹
- Egyptian hieroglyphic
- 𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓏺
- Greek (Milesian)
- ρπαʹ
- Mayan (base 20)
- 𝋩·𝋡
- Chinese
- 一百八十一
- Chinese (financial)
- 壹佰捌拾壹
Digit at this position in famous constants
- π — Pi (π)
- Digit 181 = 9
- e — Euler's number (e)
- Digit 181 = 3
- φ — Golden ratio (φ)
- Digit 181 = 8
- √2 — Pythagoras's (√2)
- Digit 181 = 9
- ln 2 — Natural log of 2
- Digit 181 = 7
- γ — Euler-Mascheroni (γ)
- Digit 181 = 3
Also seen as
UTF-8 encoding: C2 B5 (2 bytes).
As an unsigned 32-bit integer, this is the IPv4 address 0.0.0.181.
- Address
- 0.0.0.181
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.0.181
Unspecified address (0.0.0.0/8) — "this network" placeholder.
This passes the ABA routing number checksum and matches the Federal Reserve numbering scheme.
Banks operate many routing numbers per state and division; an unmatched checksum-valid number can still be a real RTN at a smaller institution.