1,661
1,661 is a composite number, odd, a calendar year.
1,661 (one thousand six hundred sixty-one) is an odd 4-digit number. It is a composite number with 4 divisors, and factors as 11 × 151. Its digits read the same forwards and backwards, so it is a palindromic number. Written other ways, in Roman numerals it is MDCLXI and in binary, 11001111101.
Interestingness
Notable events — 1661 AD
- Mar 9 Cardinal Mazarin dies; Louis XIV begins his personal rule of France.
- Sep 5 Nicolas Fouquet is arrested at Vaux-le-Vicomte.
- Jan 6 Fifth Monarchists rise in London.
Events compiled from Wikipedia ↗ · Licensed CC BY-SA 4.0
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
-
Saturday
January 1, 1661
- Ended on
-
Saturday
December 31, 1661
- Friday the 13ths
-
1
One Friday the 13th this year.
- Easter Sunday
-
April 17
Sunday, April 17, 1661
- Decade
-
1660s
1660–1669
- Century
-
17th century
1601–1700
- Millennium
-
2nd millennium
1001–2000
- Years ago
-
365
365 years before 2026.
In other calendars
- Hebrew
-
5421 / 5422 AM
Rosh Hashanah falls in September/October.
- Islamic Hijri
-
1071 / 1072 AH
Lunar calendar; year spans differ from Gregorian.
- 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
-
2204 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Persian Solar Hijri
-
1039 / 1040 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
- Ethiopian
-
1653 / 1654 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
1583 / 1582 Saka
Indian national calendar; year starts in March.
Properties
- Parity
- Odd
- Digit count
- 4
- Digit sum
- 14
- Digit product
- 36
- Digital root
- 5
- Palindrome
- Yes
- Bit width
- 11 bits
- Flips to (rotate 180°)
- 1,991
- Recamán's sequence
- a(790) = 1,661
- Square (n²)
- 2,758,921
- Cube (n³)
- 4,582,567,781
- Divisor count
- 4
- σ(n) — sum of divisors
- 1,824
- φ(n) — Euler's totient
- 1,500
- Sum of prime factors
- 162
Primality
Prime factorization: 11 × 151
Divisors & multiples
Sums & aliquot sequence
Continued fraction of √n
√1,661 = [40; (1, 3, 11, 2, 1, 1, 5, 1, 2, 15, 1, 19, 2, 3, 1, 1, 2, 2, 1, 6, 1, 2, 2, 1, …)]
Period length 40 — the block in parentheses repeats forever.
Representations
- In words
- one thousand six hundred sixty-one
- Ordinal
- 1661st
- Roman numeral
- MDCLXI
- Binary
- 11001111101
- Octal
- 3175
- Hexadecimal
- 0x67D
- Base64
- Bn0=
- One's complement
- 63,874 (16-bit)
- Scientific notation
- 1.661 × 10³
- As a duration
- 1,661 s = 27 minutes, 41 seconds
As an angle
Historical numeral systems
- Babylonian (base 60)
- 𒌋𒌋𒁹𒁹𒁹𒁹𒁹𒁹𒁹 𒌋𒌋𒌋𒌋𒁹
- Egyptian hieroglyphic
- 𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓏺
- Greek (Milesian)
- ͵αχξαʹ
- Mayan (base 20)
- 𝋤·𝋣·𝋡
- Chinese
- 一千六百六十一
- Chinese (financial)
- 壹仟陸佰陸拾壹
Digit at this position in famous constants
- π — Pi (π)
- Digit 1,661 = 3
- e — Euler's number (e)
- Digit 1,661 = 4
- φ — Golden ratio (φ)
- Digit 1,661 = 8
- √2 — Pythagoras's (√2)
- Digit 1,661 = 5
- ln 2 — Natural log of 2
- Digit 1,661 = 8
- γ — Euler-Mascheroni (γ)
- Digit 1,661 = 1
Also seen as
UTF-8 encoding: D9 BD (2 bytes).
As an unsigned 32-bit integer, this is the IPv4 address 0.0.6.125.
- Address
- 0.0.6.125
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.6.125
Unspecified address (0.0.0.0/8) — "this network" placeholder.
Heard as a frequency, 1,661 Hz is closest to:
- Concert pitch (A4 = 440 Hz): G♯6 (1661.2 Hz, exact)
- Scientific pitch (C4 = 256 Hz): G♯6 (1625.5 Hz, +37¢)
- Baroque pitch (A4 = 415 Hz): A6 (1660 Hz, +1¢)
The digit sequence 1661 first appears in π at position 2,746 of the decimal expansion (the 2,746ordinal-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.
Related reading
- Mayan numerals — Vigesimal dots-and-bars with a shell zero — one of the earliest true zeros.