1,721
1,721 is a prime, odd, a calendar year.
1,721 (one thousand seven hundred twenty-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 MDCCXXI and in binary, 11010111001.
Interestingness
Notable events — 1721 AD
- Sep 10 The Treaty of Nystad ends the Great Northern War; Russia becomes a great power.
- Nov 2 Peter the Great is proclaimed Emperor of All Russia.
- Apr 4 Robert Walpole becomes Britain's effective first prime minister.
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
-
Wednesday
January 1, 1721
- Ended on
-
Wednesday
December 31, 1721
- Friday the 13ths
-
1
One Friday the 13th this year.
- Easter Sunday
-
April 13
Sunday, April 13, 1721
- Decade
-
1720s
1720–1729
- Century
-
18th century
1701–1800
- Millennium
-
2nd millennium
1001–2000
- Years ago
-
305
305 years before 2026.
In other calendars
- Hebrew
-
5481 / 5482 AM
Rosh Hashanah falls in September/October.
- Islamic Hijri
-
1133 / 1134 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
-
2264 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Persian Solar Hijri
-
1099 / 1100 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
- Ethiopian
-
1713 / 1714 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
1643 / 1642 Saka
Indian national calendar; year starts in March.
Properties
Primality
1,721 is prime. It has exactly two divisors: 1 and itself.
Divisors & multiples
Sums & aliquot sequence
Continued fraction of √n
√1,721 = [41; (2, 16, 10, 3, 4, 1, 1, 3, 1, 4, 2, 2, 7, 7, 2, 2, 4, 1, 3, 1, 1, 4, 3, 10, …)]
Period length 27 — the block in parentheses repeats forever.
Representations
- In words
- one thousand seven hundred twenty-one
- Ordinal
- 1721st
- Roman numeral
- MDCCXXI
- Binary
- 11010111001
- Octal
- 3271
- Hexadecimal
- 0x6B9
- Base64
- Brk=
- One's complement
- 63,814 (16-bit)
- Scientific notation
- 1.721 × 10³
- As a duration
- 1,721 s = 28 minutes, 41 seconds
As an angle
Historical numeral systems
- Babylonian (base 60)
- 𒌋𒌋𒁹𒁹𒁹𒁹𒁹𒁹𒁹𒁹 𒌋𒌋𒌋𒌋𒁹
- Egyptian hieroglyphic
- 𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓏺
- Greek (Milesian)
- ͵αψκαʹ
- Mayan (base 20)
- 𝋤·𝋦·𝋡
- Chinese
- 一千七百二十一
- Chinese (financial)
- 壹仟柒佰貳拾壹
Digit at this position in famous constants
- π — Pi (π)
- Digit 1,721 = 5
- e — Euler's number (e)
- Digit 1,721 = 4
- φ — Golden ratio (φ)
- Digit 1,721 = 6
- √2 — Pythagoras's (√2)
- Digit 1,721 = 2
- ln 2 — Natural log of 2
- Digit 1,721 = 6
- γ — Euler-Mascheroni (γ)
- Digit 1,721 = 3
Also seen as
UTF-8 encoding: DA B9 (2 bytes).
As an unsigned 32-bit integer, this is the IPv4 address 0.0.6.185.
- Address
- 0.0.6.185
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.6.185
Unspecified address (0.0.0.0/8) — "this network" placeholder.
Heard as a frequency, 1,721 Hz is closest to:
- Concert pitch (A4 = 440 Hz): A6 (1760 Hz, -39¢)
- Scientific pitch (C4 = 256 Hz): A6 (1722.2 Hz, -1¢)
- Baroque pitch (A4 = 415 Hz): A♯6 (1758.7 Hz, -38¢)
The digit sequence 1721 first appears in π at position 1,419 of the decimal expansion (the 1,419ordinal-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
- Prime numbers — The building blocks of arithmetic: what primes are, why they matter, and how we find them.
- Mayan numerals — Vigesimal dots-and-bars with a shell zero — one of the earliest true zeros.