Number

720

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

720 (seven hundred twenty) is an even 3-digit number. It is a composite number with 30 divisors, and factors as 2⁴ × 3² × 5. Its proper divisors sum to 1,698, more than the number itself, making it an abundant number. It is a factorial (6! = 720). Written other ways, in Roman numerals it is DCCXX and in binary, 1011010000.

Abundant Number Descending Digits Evil Number Factorial Harshad / Niven Highly Abundant Highly Composite Number Practical Number Recamán's Sequence Refactorable Number Semiperfect Number Year

Interestingness

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9 notable facts · grade A

708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732

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Historical context — 720 AD

Calendar year

Year 720 (DCCXX) was a leap year starting on Monday of the Julian calendar.

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

Historical context — 720 BC

Decade

This article concerns the period 729 BC – 720 BC.

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

Year facts

Year type: Leap year
Divisible by 4 and not by 100; February has 29 days.
Days in year: 366
ISO weeks: 53
Long year: contains 53 ISO weeks.
Started on: Thursday
January 1, 720
Ended on: Friday
December 31, 720
Friday the 13ths: 2
2 Friday the 13ths this year.
Decade: 720s
720–729
Century: 8th century
701–800
Millennium: 1st millennium
1–1000
Years ago: 1,306
1306 years before 2026.

In other calendars

Hebrew: 4480 / 4481 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 101 / 102 AH
Lunar calendar; year spans differ from Gregorian.
Chinese: Year of the zodiac:Metal zodiac:Monkey
Sexagenary cycle position 57 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 1263 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 98 / 99 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 712 / 713 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 642 / 641 Saka
Indian national calendar; year starts in March.

Properties

Parity: Even
Digit count: 3
Digit sum: 9
Digit product: 0
Digital root: 9
Palindrome: No
Bit width: 10 bits
Reversed: 27
Recamán's sequence: a(227) = 720
Square (n²): 518,400
Cube (n³): 373,248,000
Divisor count: 30
σ(n) — sum of divisors: 2,418
φ(n) — Euler's totient: 192
Sum of prime factors: 19

Primality

Prime factorization: 2 ⁴ × 3 ² × 5

Nearest primes: 719 (−1) · 727 (+7)

Divisors & multiples

All divisors (30)

1 · 2 · 3 · 4 · 5 · 6 · 8 · 9 · 10 · 12 · 15 · 16 · 18 · 20 · 24 · 30 · 36 · 40 · 45 · 48 · 60 · 72 · 80 · 90 · 120 · 144 · 180 · 240 · 360 (half) · 720

Aliquot sum (sum of proper divisors): 1,698

Factor pairs (a × b = 720)

1 × 720

2 × 360

3 × 240

4 × 180

5 × 144

6 × 120

8 × 90

9 × 80

10 × 72

12 × 60

15 × 48

16 × 45

18 × 40

20 × 36

24 × 30

First multiples

720 · 1,440 (double) · 2,160 · 2,880 · 3,600 · 4,320 · 5,040 · 5,760 · 6,480 · 7,200

Sums & aliquot sequence

As a sum of two squares: 12² + 24²

As consecutive integers: 239 + 240 + 241 142 + 143 + 144 + 145 + 146 76 + 77 + … + 84 41 + 42 + … + 55

Aliquot sequence: 720 → 1,698 → 1,710 → 2,970 → 5,670 → 11,754 → 13,752 → 23,688 → 51,192 → 94,008 → 141,072 → 223,488 → 427,526 → 272,098 → 147,194 → 73,600 → 116,120 — unresolved within range

Continued fraction of √n

√720 = [26; (1, 4, 1, 52)]

Period length 4 — the block in parentheses repeats forever.

Representations

In words: seven hundred twenty
Ordinal: 720th
Roman numeral: DCCXX
Binary: 1011010000
Octal: 1320
Hexadecimal: 0x2D0
Base64: AtA=
One's complement: 64,815 (16-bit)
Scientific notation: 7.2 × 10²
As a duration: 720 s = 12 minutes

In other bases

ternary (3) 222200

quaternary (4) 23100

quinary (5) 10340

senary (6) 3200

septenary (7) 2046

nonary (9) 880

undecimal (11) 5a5

duodecimal (12) 500

tridecimal (13) 435

tetradecimal (14) 396

pentadecimal (15) 330

Palindromic in base 11

As an angle

720° = 2 × 360°

0° ≈ 0 rad

Compass bearing: N (north)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒌋𒁹𒁹 ·
Egyptian hieroglyphic: 𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆
Greek (Milesian): ψκʹ
Mayan (base 20): 𝋡·𝋰·𝋠
Chinese: 七百二十
Chinese (financial): 柒佰貳拾

In other modern scripts

Eastern Arabic ٧٢٠ Devanagari ७२० Bengali ৭২০ Tamil ௭௨௦ Thai ๗๒๐ Tibetan ༧༢༠ Khmer ៧២០ Lao ໗໒໐ Burmese ၇၂၀

Digit at this position in famous constants

π — Pi (π): Digit 720 = 6
e — Euler's number (e): Digit 720 = 5
φ — Golden ratio (φ): Digit 720 = 8
√2 — Pythagoras's (√2): Digit 720 = 0
ln 2 — Natural log of 2: Digit 720 = 3
γ — Euler-Mascheroni (γ): Digit 720 = 3

Also seen as

Goldbach decomposition

Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 720, here are decompositions:

11 + 709 = 720
19 + 701 = 720
29 + 691 = 720
37 + 683 = 720
43 + 677 = 720
47 + 673 = 720
59 + 661 = 720
61 + 659 = 720

Showing the first eight; more decompositions exist.

Unicode codepoint

Modifier Letter Triangular Colon

U+02D0

Modifier letter (Lm)

UTF-8 encoding: CB 90 (2 bytes).

Lookup U+02D0 on Compart ↗ Lookup on FileFormat.Info ↗

Code page identifier

Code page 720 is DOS Arabic — DOS code page for Arabic.

Code pages are integer identifiers used by Windows and other systems to refer to specific character encodings.

Microsoft code page reference ↗

Hex color

#0002D0

RGB(0, 2, 208)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.2.208.

Address: 0.0.2.208
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.2.208

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

NANP area code 720

The number 720 is an active NANP area code (North American Numbering Plan).

Primary area: Denver
Region: Colorado
Country: United States

Most NANP area codes have multiple overlays in dense regions; the primary area listed is the historic/largest population center for this code.

Look up area code 720 ↗

Musical pitch

Heard as a frequency, 720 Hz is closest to:

Concert pitch (A4 = 440 Hz): F♯5 (740 Hz, -47¢ — about midway to F5)
Scientific pitch (C4 = 256 Hz): F♯5 (724.1 Hz, -10¢)
Baroque pitch (A4 = 415 Hz): G5 (739.4 Hz, -46¢ — about midway to F♯5)