Number

642

642 is a composite number, even, a calendar year.

642 (six hundred forty-two) is an even 3-digit number. It is a composite number with 8 divisors, and factors as 2 × 3 × 107. Its proper divisors sum to 654, more than the number itself, making it an abundant number. Written other ways, in Roman numerals it is DCXLII and in binary, 1010000010.

Abundant Number Arithmetic Number Cube-Free Descending Digits Odious Number Pernicious Number Recamán's Sequence Semiperfect Number Sphenic Number Squarefree Stepped Digits Year

Interestingness

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8 notable facts · grade A

630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654

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Historical context — 642 AD

Calendar year

Year 642 (DCXLII) was a common year starting on Tuesday of the Julian calendar.

Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 Read the full article on Wikipedia →

Historical context — 642 BC

Calendar year

The year 642 BC was a year of the pre-Julian Roman calendar.

Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 Read the full article on Wikipedia →

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, 642
Ended on: Saturday
December 31, 642
Friday the 13ths: 1
One Friday the 13th this year.
Decade: 640s
640–649
Century: 7th century
601–700
Millennium: 1st millennium
1–1000
Years ago: 1,384
1384 years before 2026.

In other calendars

Hebrew: 4402 / 4403 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 21 / 22 AH
Lunar calendar; year spans differ from Gregorian.
Chinese: Year of the zodiac:Water zodiac:Tiger
Sexagenary cycle position 39 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 1185 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 20 / 21 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 634 / 635 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 564 / 563 Saka
Indian national calendar; year starts in March.

Properties

Parity: Even
Digit count: 3
Digit sum: 12
Digit product: 48
Digital root: 3
Palindrome: No
Bit width: 10 bits
Reversed: 246
Recamán's sequence: a(191) = 642
Square (n²): 412,164
Cube (n³): 264,609,288
Divisor count: 8
σ(n) — sum of divisors: 1,296
φ(n) — Euler's totient: 212
Sum of prime factors: 112

Primality

Prime factorization: 2 × 3 × 107

Nearest primes: 641 (−1) · 643 (+1)

Divisors & multiples

All divisors (8)

1 · 2 · 3 · 6 · 107 · 214 · 321 (half) · 642

Aliquot sum (sum of proper divisors): 654

Factor pairs (a × b = 642)

1 × 642

2 × 321

3 × 214

6 × 107

First multiples

642 · 1,284 (double) · 1,926 · 2,568 · 3,210 · 3,852 · 4,494 · 5,136 · 5,778 · 6,420

Sums & aliquot sequence

As consecutive integers: 213 + 214 + 215 159 + 160 + 161 + 162 48 + 49 + … + 59

Aliquot sequence: 642 → 654 → 666 → 816 → 1,416 → 2,184 → 4,536 → 9,984 → 18,632 → 18,628 → 13,978 → 7,802 → 4,294 → 2,546 → 1,534 → 986 → 634 — unresolved within range

Continued fraction of √n

√642 = [25; (2, 1, 24, 1, 2, 50)]

Period length 6 — the block in parentheses repeats forever.

Representations

In words: six hundred forty-two
Ordinal: 642nd
Roman numeral: DCXLII
Binary: 1010000010
Octal: 1202
Hexadecimal: 0x282
Base64: AoI=
One's complement: 64,893 (16-bit)
Scientific notation: 6.42 × 10²
As a duration: 642 s = 10 minutes, 42 seconds

In other bases

ternary (3) 212210

quaternary (4) 22002

quinary (5) 10032

senary (6) 2550

septenary (7) 1605

nonary (9) 783

undecimal (11) 534

duodecimal (12) 456

tridecimal (13) 3a5

tetradecimal (14) 33c

pentadecimal (15) 2cc

Palindromic in base 16

As an angle

642° = 1 × 360° + 282°

282° ≈ 4.922 rad

Compass bearing: WNW (west-northwest)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒌋 𒌋𒌋𒌋𒌋𒁹𒁹
Egyptian hieroglyphic: 𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓏺𓏺
Greek (Milesian): χμβʹ
Mayan (base 20): 𝋡·𝋬·𝋢
Chinese: 六百四十二
Chinese (financial): 陸佰肆拾貳

In other modern scripts

Eastern Arabic ٦٤٢ Devanagari ६४२ Bengali ৬৪২ Tamil ௬௪௨ Thai ๖๔๒ Tibetan ༦༤༢ Khmer ៦៤២ Lao ໖໔໒ Burmese ၆၄၂

Digit at this position in famous constants

π — Pi (π): Digit 642 = 7
e — Euler's number (e): Digit 642 = 7
φ — Golden ratio (φ): Digit 642 = 1
√2 — Pythagoras's (√2): Digit 642 = 9
ln 2 — Natural log of 2: Digit 642 = 4
γ — Euler-Mascheroni (γ): Digit 642 = 9

Also seen as

Goldbach decomposition

Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 642, here are decompositions:

11 + 631 = 642
23 + 619 = 642
29 + 613 = 642
41 + 601 = 642
43 + 599 = 642
71 + 571 = 642
73 + 569 = 642
79 + 563 = 642

Showing the first eight; more decompositions exist.

Unicode codepoint

Latin Small Letter S With Hook

U+0282

Lowercase letter (Ll)

UTF-8 encoding: CA 82 (2 bytes).

Lookup U+0282 on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#000282

RGB(0, 2, 130)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.2.130.

Address: 0.0.2.130
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.2.130

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

Musical pitch

Heard as a frequency, 642 Hz is closest to:

Concert pitch (A4 = 440 Hz): E5 (659.3 Hz, -46¢ — about midway to D♯5)
Scientific pitch (C4 = 256 Hz): E5 (645.1 Hz, -8¢)
Baroque pitch (A4 = 415 Hz): F5 (658.8 Hz, -45¢ — about midway to E5)