Number

728

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

728 (seven hundred twenty-eight) is an even 3-digit number. It is a composite number with 16 divisors, and factors as 2³ × 7 × 13. Its proper divisors sum to 952, more than the number itself, making it an abundant number. Written other ways, in Roman numerals it is DCCXXVIII and in binary, 1011011000.

Abundant Number Arithmetic Number Odious Number Pernicious Number Practical Number Recamán's Sequence Semiperfect Number Smith Number Year

Interestingness

★ ★ ★ ☆ ☆

5 notable facts · grade C

716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740

less more

Historical context — 728 AD

Calendar year

Year 728 (DCCXXVIII) was a leap year starting on Thursday of the Julian calendar.

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

Historical context — 728 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: 52
Started on: Sunday
January 1, 728
Ended on: Monday
December 31, 728
Friday the 13ths: 3
3 Friday the 13ths this year.
Decade: 720s
720–729
Century: 8th century
701–800
Millennium: 1st millennium
1–1000
Years ago: 1,298
1298 years before 2026.

In other calendars

Hebrew: 4488 / 4489 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 109 / 110 AH
Lunar calendar; year spans differ from Gregorian.
Chinese: Year of the zodiac:Earth zodiac:Dragon
Sexagenary cycle position 5 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 1271 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 106 / 107 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 720 / 721 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 650 / 649 Saka
Indian national calendar; year starts in March.

Properties

Parity: Even
Digit count: 3
Digit sum: 17
Digit product: 112
Digital root: 8
Palindrome: No
Bit width: 10 bits
Reversed: 827
Recamán's sequence: a(975) = 728
Square (n²): 529,984
Cube (n³): 385,828,352
Divisor count: 16
σ(n) — sum of divisors: 1,680
φ(n) — Euler's totient: 288
Sum of prime factors: 26

Primality

Prime factorization: 2 ³ × 7 × 13

Nearest primes: 727 (−1) · 733 (+5)

Divisors & multiples

All divisors (16)

1 · 2 · 4 · 7 · 8 · 13 · 14 · 26 · 28 · 52 · 56 · 91 · 104 · 182 · 364 (half) · 728

Aliquot sum (sum of proper divisors): 952

Factor pairs (a × b = 728)

1 × 728

2 × 364

4 × 182

7 × 104

8 × 91

13 × 56

14 × 52

26 × 28

First multiples

728 · 1,456 (double) · 2,184 · 2,912 · 3,640 · 4,368 · 5,096 · 5,824 · 6,552 · 7,280

Sums & aliquot sequence

As a sum of two cubes: 6³ + 8³

As consecutive integers: 101 + 102 + … + 107 50 + 51 + … + 62 38 + 39 + … + 53

Aliquot sequence: 728 → 952 → 1,208 → 1,072 → 1,036 → 1,092 → 2,044 → 2,100 → 4,844 → 4,900 → 7,469 → 1,939 → 285 → 195 → 141 → 51 → 21 — unresolved within range

Continued fraction of √n

√728 = [26; (1, 52)]

Period length 2 — the block in parentheses repeats forever.

Representations

In words: seven hundred twenty-eight
Ordinal: 728th
Roman numeral: DCCXXVIII
Binary: 1011011000
Octal: 1330
Hexadecimal: 0x2D8
Base64: Atg=
One's complement: 64,807 (16-bit)
Scientific notation: 7.28 × 10²
As a duration: 728 s = 12 minutes, 8 seconds

In other bases

ternary (3) 222222

quaternary (4) 23120

quinary (5) 10403

senary (6) 3212

septenary (7) 2060

nonary (9) 888

undecimal (11) 602

duodecimal (12) 508

tridecimal (13) 440

tetradecimal (14) 3a0

pentadecimal (15) 338

Palindromic in base 3, base 9

As an angle

728° = 2 × 360° + 8°

8° ≈ 0.14 rad

Compass bearing: N (north)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒌋𒁹𒁹 𒁹𒁹𒁹𒁹𒁹𒁹𒁹𒁹
Egyptian hieroglyphic: 𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓏺𓏺𓏺𓏺𓏺𓏺𓏺𓏺
Greek (Milesian): ψκηʹ
Mayan (base 20): 𝋡·𝋰·𝋨
Chinese: 七百二十八
Chinese (financial): 柒佰貳拾捌

In other modern scripts

Eastern Arabic ٧٢٨ Devanagari ७२८ Bengali ৭২৮ Tamil ௭௨௮ Thai ๗๒๘ Tibetan ༧༢༨ Khmer ៧២៨ Lao ໗໒໘ Burmese ၇၂၈

Digit at this position in famous constants

π — Pi (π): Digit 728 = 4
e — Euler's number (e): Digit 728 = 5
φ — Golden ratio (φ): Digit 728 = 4
√2 — Pythagoras's (√2): Digit 728 = 1
ln 2 — Natural log of 2: Digit 728 = 6
γ — Euler-Mascheroni (γ): Digit 728 = 5

Also seen as

Goldbach decomposition

Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 728, here are decompositions:

19 + 709 = 728
37 + 691 = 728
67 + 661 = 728
97 + 631 = 728
109 + 619 = 728
127 + 601 = 728
151 + 577 = 728
157 + 571 = 728

Showing the first eight; more decompositions exist.

Unicode codepoint

Breve

U+02D8

Modifier symbol (Sk)

UTF-8 encoding: CB 98 (2 bytes).

Lookup U+02D8 on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#0002D8

RGB(0, 2, 216)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.2.216.

Address: 0.0.2.216
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.2.216

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

Musical pitch

Heard as a frequency, 728 Hz is closest to:

Concert pitch (A4 = 440 Hz): F♯5 (740 Hz, -28¢)
Scientific pitch (C4 = 256 Hz): F♯5 (724.1 Hz, +9¢)
Baroque pitch (A4 = 415 Hz): G5 (739.4 Hz, -27¢)