1,666
1,666 is a composite number, even, a calendar year.
Notable events — 1666 AD
- Sep 2 The Great Fire of London destroys much of the city.
- Apr 30 Isaac Newton begins his "miracle years" of scientific discovery while sheltering from the plague.
- Sep 5 King Charles II returns to a still-burning 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
-
Friday
January 1, 1666
- Ended on
-
Friday
December 31, 1666
- Friday the 13ths
-
1
One Friday the 13th this year.
- Easter Sunday
-
April 25
Sunday, April 25, 1666
- Decade
-
1660s
1660–1669
- Century
-
17th century
1601–1700
- Millennium
-
2nd millennium
1001–2000
- Years ago
-
360
360 years before 2026.
In other calendars
- Hebrew
-
5426 / 5427 AM
Rosh Hashanah falls in September/October.
- Islamic Hijri
-
1076 / 1077 AH
Lunar calendar; year spans differ from Gregorian.
- Chinese
-
Year of the zodiac:Fire zodiac:Horse
Sexagenary cycle position 43 of 60. Lunar new year falls in late January / mid-February.
- Buddhist Era
-
2209 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Persian Solar Hijri
-
1044 / 1045 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
- Ethiopian
-
1658 / 1659 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
1588 / 1587 Saka
Indian national calendar; year starts in March.
Properties
- Parity
- Even
- Digit count
- 4
- Digit sum
- 19
- Digit product
- 216
- Digital root
- 1
- Palindrome
- No
- Bit width
- 11 bits
- Reversed
- 6,661
- Flips to (rotate 180°)
- 9,991
- Recamán's sequence
- a(800) = 1,666
- Square (n²)
- 2,775,556
- Cube (n³)
- 4,624,076,296
- Divisor count
- 12
- σ(n) — sum of divisors
- 3,078
- φ(n) — Euler's totient
- 672
- Sum of prime factors
- 33
Primality
Prime factorization: 2 × 7 2 × 17
Divisors & multiples
Sums & aliquot sequence
Representations
- In words
- one thousand six hundred sixty-six
- Ordinal
- 1666th
- Roman numeral
- MDCLXVI
- Binary
- 11010000010
- Octal
- 3202
- Hexadecimal
- 0x682
- Base64
- BoI=
- One's complement
- 63,869 (16-bit)
Historical numeral systems
- Babylonian (base 60)
- 𒌋𒌋𒁹𒁹𒁹𒁹𒁹𒁹𒁹 𒌋𒌋𒌋𒌋𒁹𒁹𒁹𒁹𒁹𒁹
- Egyptian hieroglyphic
- 𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓏺𓏺𓏺𓏺𓏺𓏺
- Greek (Milesian)
- ͵αχξϛʹ
- Mayan (base 20)
- 𝋤·𝋣·𝋦
- Chinese
- 一千六百六十六
- Chinese (financial)
- 壹仟陸佰陸拾陸
Digit at this position in famous constants
- π — Pi (π)
- Digit 1,666 = 2
- e — Euler's number (e)
- Digit 1,666 = 2
- φ — Golden ratio (φ)
- Digit 1,666 = 3
- √2 — Pythagoras's (√2)
- Digit 1,666 = 3
- ln 2 — Natural log of 2
- Digit 1,666 = 0
- γ — Euler-Mascheroni (γ)
- Digit 1,666 = 5
Also seen as
Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 1666, here are decompositions:
- 3 + 1663 = 1666
- 29 + 1637 = 1666
- 47 + 1619 = 1666
- 53 + 1613 = 1666
- 59 + 1607 = 1666
- 83 + 1583 = 1666
- 107 + 1559 = 1666
- 113 + 1553 = 1666
Showing the first eight; more decompositions exist.
UTF-8 encoding: DA 82 (2 bytes).
As an unsigned 32-bit integer, this is the IPv4 address 0.0.6.130.
- Address
- 0.0.6.130
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.6.130
Unspecified address (0.0.0.0/8) — "this network" placeholder.
The digit sequence 1666 first appears in π at position 5,402 of the decimal expansion (the 5,402ordinal-suffix:nd 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.