Number
1,721
1,721 is a prime, odd, a calendar year.
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
Aliquot sum (sum of proper divisors):
1
First multiples
Sums & aliquot sequence
As a sum of two squares:
11² + 40²
As consecutive integers:
860 + 861
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)
In other bases
ternary (3)
2100202
quaternary (4)
122321
quinary (5)
23341
senary (6)
11545
septenary (7)
5006
nonary (9)
2322
undecimal (11)
1325
duodecimal (12)
bb5
tridecimal (13)
a25
tetradecimal (14)
8ad
pentadecimal (15)
79b
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
In other modern scripts
Eastern Arabic
١٧٢١
Devanagari
१७२१
Bengali
১৭২১
Tamil
௧௭௨௧
Thai
๑๗๒๑
Tibetan
༡༧༢༡
Khmer
១៧២១
Lao
໑໗໒໑
Burmese
၁၇၂၁
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
Prime neighborhood
Unicode codepoint
ڹ
Arabic Letter Noon With Dot Below
U+06B9
Other letter (Lo)
UTF-8 encoding: DA B9 (2 bytes).
Hex color
#0006B9
RGB(0, 6, 185)
IPv4 address
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.
Position in π
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.