Number

3,821

3,821 is a prime, odd.

3,821 (three thousand eight 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 MMMDCCCXXI and in binary, 111011101101.

Arithmetic Number Chen Prime Cube-Free Deficient Number Emirp Odious Number Prime Pythagorean Prime Recamán's Sequence Sophie Germain Prime Squarefree Twin Prime

Interestingness

★ ★ ★ ★ ★

10 notable facts · grade A

3,809 3,810 3,811 3,812 3,813 3,814 3,815 3,816 3,817 3,818 3,819 3,820 3,821 3,822 3,823 3,824 3,825 3,826 3,827 3,828 3,829 3,830 3,831 3,832 3,833

less more

Properties

Parity: Odd
Digit count: 4
Digit sum: 14
Digit product: 48
Digital root: 5
Palindrome: No
Bit width: 12 bits
Reversed: 1,283
Recamán's sequence: a(6,286) = 3,821
Square (n²): 14,600,041
Cube (n³): 55,786,756,661
Divisor count: 2
σ(n) — sum of divisors: 3,822
φ(n) — Euler's totient: 3,820

Primality

3,821 is prime. It has exactly two divisors: 1 and itself.

Divisors & multiples

All divisors (2)

1 · 3821

Aliquot sum (sum of proper divisors): 1

Factor pairs (a × b = 3,821)

1 × 3821

First multiples

3,821 · 7,642 (double) · 11,463 · 15,284 · 19,105 · 22,926 · 26,747 · 30,568 · 34,389 · 38,210

Sums & aliquot sequence

As a sum of two squares: 10² + 61²

As consecutive integers: 1,910 + 1,911

Continued fraction of √n

√3,821 = [61; (1, 4, 2, 1, 1, 1, 1, 3, 1, 1, 1, 5, 1, 1, 5, 1, 1, 1, 3, 1, 1, 1, 1, 2, …)]

Period length 27 — the block in parentheses repeats forever.

Representations

In words: three thousand eight hundred twenty-one
Ordinal: 3821st
Roman numeral: MMMDCCCXXI
Binary: 111011101101
Octal: 7355
Hexadecimal: 0xEED
Base64: Du0=
One's complement: 61,714 (16-bit)
Scientific notation: 3.821 × 10³
As a duration: 3,821 s = 1 hour, 3 minutes, 41 seconds

In other bases

ternary (3) 12020112

quaternary (4) 323231

quinary (5) 110241

senary (6) 25405

septenary (7) 14066

nonary (9) 5215

undecimal (11) 2964

duodecimal (12) 2265

tridecimal (13) 197c

tetradecimal (14) 156d

pentadecimal (15) 11eb

As an angle

3,821° = 10 × 360° + 221°

221° ≈ 3.857 rad

Compass bearing: SW (southwest)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒁹 𒁹𒁹𒁹 𒌋𒌋𒌋𒌋𒁹
Egyptian hieroglyphic: 𓆼𓆼𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓏺
Greek (Milesian): ͵γωκαʹ
Mayan (base 20): 𝋩·𝋫·𝋡
Chinese: 三千八百二十一
Chinese (financial): 參仟捌佰貳拾壹

In other modern scripts

Eastern Arabic ٣٨٢١ Devanagari ३८२१ Bengali ৩৮২১ Tamil ௩௮௨௧ Thai ๓๘๒๑ Tibetan ༣༨༢༡ Khmer ៣៨២១ Lao ໓໘໒໑ Burmese ၃၈၂၁

Digit at this position in famous constants

π — Pi (π): Digit 3,821 = 9
e — Euler's number (e): Digit 3,821 = 5
φ — Golden ratio (φ): Digit 3,821 = 2
√2 — Pythagoras's (√2): Digit 3,821 = 5
ln 2 — Natural log of 2: Digit 3,821 = 4
γ — Euler-Mascheroni (γ): Digit 3,821 = 8

Also seen as

Prime neighborhood

Adjacent primes:

Previous prime: 3,803 (gap of 18)
Next prime: 3,823 (gap of 2)

Pair status: twin with 3823.

Hex color

#000EED

RGB(0, 14, 237)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.14.237.

Address: 0.0.14.237
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.14.237

Unspecified address (0.0.0.0/8) — "this network" placeholder.

Musical pitch

Heard as a frequency, 3,821 Hz is closest to:

Concert pitch (A4 = 440 Hz): A♯7 (3729.3 Hz, +42¢)
Scientific pitch (C4 = 256 Hz): B7 (3866.1 Hz, -20¢)
Baroque pitch (A4 = 415 Hz): B7 (3726.6 Hz, +43¢)

Position in π

The digit sequence 3821 first appears in π at position 13,418 of the decimal expansion (the 13,418ordinal-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.

Look up 3821 on Pi Search ↗