Number

78

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

Abundant Number Arithmetic Number Evil Number Practical Number Recamán's Sequence Semiperfect Number Sphenic Number Squarefree Triangular Year

Historical context — 78 AD

Calendar year

AD 78 (LXXVIII) was a common year starting on Thursday of the Julian calendar.

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Historical context — 78 BC

Calendar year

Year 78 BC was a year of the pre-Julian Roman calendar.

Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 · English fallback 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, 78
Ended on: Saturday
December 31, 78
Friday the 13ths: 1
One Friday the 13th this year.
Decade: 70s
70–79
Century: 1st century
1–100
Millennium: 1st millennium
1–1000
Years ago: 1,948
1948 years before 2026.

In other calendars

Hebrew: 3838 / 3839 AM
Rosh Hashanah falls in September/October.
Chinese: Year of the zodiac:Earth zodiac:Tiger
Sexagenary cycle position 15 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 621 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Ethiopian: 70 / 71 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 0 / -1 Saka
Indian national calendar; year starts in March.

Properties

Parity: Even
Digit count: 2
Digit sum: 15
Digit product: 56
Digital root: 6
Palindrome: No
Bit width: 7 bits
Reversed: 87
Recamán's sequence: a(35) = 78
Square (n²): 6,084
Cube (n³): 474,552
Divisor count: 8
σ(n) — sum of divisors: 168
φ(n) — Euler's totient: 24
Sum of prime factors: 18

Primality

Prime factorization: 2 × 3 × 13

Nearest primes: 73 (−5) · 79 (+1)

Divisors & multiples

All divisors (8)

1 · 2 · 3 · 6 · 13 · 26 · 39 (half) · 78

Aliquot sum (sum of proper divisors): 90

Factor pairs (a × b = 78)

1 × 78

2 × 39

3 × 26

6 × 13

First multiples

78 · 156 (double) · 234 · 312 · 390 · 468 · 546 · 624 · 702 · 780

Sums & aliquot sequence

As consecutive integers: 25 + 26 + 27 18 + 19 + 20 + 21 1 + 2 + … + 12

Aliquot sequence: 78 → 90 → 144 → 259 → 45 → 33 → 15 → 9 → 4 → 3 → 1 → 0 — terminates at zero

Representations

In words: seventy-eight
Ordinal: 78th
Roman numeral: LXXVIII
Binary: 1001110
Octal: 116
Hexadecimal: 0x4E
Base64: Tg==
One's complement: 177 (8-bit)
Scientific notation: 7.8 × 10¹

In other bases

ternary (3) 2220

quaternary (4) 1032

quinary (5) 303

senary (6) 210

septenary (7) 141

nonary (9) 86

undecimal (11) 71

duodecimal (12) 66

tridecimal (13) 60

tetradecimal (14) 58

pentadecimal (15) 53

Palindromic in base 5, base 7

Historical numeral systems

Babylonian (base 60): 𒁹 𒌋𒁹𒁹𒁹𒁹𒁹𒁹𒁹𒁹
Egyptian hieroglyphic: 𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓏺𓏺𓏺𓏺𓏺𓏺𓏺𓏺
Greek (Milesian): οηʹ
Mayan (base 20): 𝋣·𝋲
Chinese: 七十八
Chinese (financial): 柒拾捌

In other modern scripts

Eastern Arabic ٧٨ Devanagari ७८ Bengali ৭৮ Tamil ௭௮ Thai ๗๘ Tibetan ༧༨ Khmer ៧៨ Lao ໗໘ Burmese ၇၈

Digit at this position in famous constants

π — Pi (π): Digit 78 = 0
e — Euler's number (e): Digit 78 = 4
φ — Golden ratio (φ): Digit 78 = 0
√2 — Pythagoras's (√2): Digit 78 = 0
ln 2 — Natural log of 2: Digit 78 = 9
γ — Euler-Mascheroni (γ): Digit 78 = 6

Also seen as

Goldbach decomposition

Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 78, here are decompositions:

5 + 73 = 78
7 + 71 = 78
11 + 67 = 78
17 + 61 = 78
19 + 59 = 78
31 + 47 = 78
37 + 41 = 78

ASCII character

As an ASCII codepoint, 78 is N. Printable ASCII character N.

Hex color

#00004E

RGB(0, 0, 78)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.0.78.

Address: 0.0.0.78
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.0.78

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

US numbered highway

Matches numbered highway designation:

I-78 — Union Township, PA to Holland Tunnel, NYC.

Interstate 78 on Wikipedia ↗