25
25 is a composite number, odd, a calendar year.
25 (twenty-five) is an odd 2-digit number. It is a composite number with 3 divisors, and factors as 5². It is a perfect square (5²). Written other ways, in Roman numerals it is XXV and in binary, 11001.
Interestingness
Historical context — 25 AD
Calendar year
AD 25 (XXV) was a common year starting on Monday of the Julian calendar.
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Historical context — 25 BC
Calendar year
Year 25 BC was either a common year starting on Wednesday, Thursday or Friday or a leap year starting on Wednesday or Thursday of the Julian calendar and a leap year starting on Tuesday of the Proleptic Julian calendar.
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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
-
Wednesday
January 1, 25
- Ended on
-
Wednesday
December 31, 25
- Friday the 13ths
-
1
One Friday the 13th this year.
- Decade
-
20s
20–29
- Century
-
1st century
1–100
- Millennium
-
1st millennium
1–1000
- Years ago
-
2,001
2001 years before 2026.
In other calendars
- Hebrew
-
3785 / 3786 AM
Rosh Hashanah falls in September/October.
- Chinese
-
Year of the zodiac:Wood zodiac:Rooster
Sexagenary cycle position 22 of 60. Lunar new year falls in late January / mid-February.
- Buddhist Era
-
568 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Ethiopian
-
17 / 18 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
-53 / -54 Saka
Indian national calendar; year starts in March.
Properties
Primality
Prime factorization: 5 2
Divisors & multiples
Sums & aliquot sequence
Representations
- In words
- twenty-five
- Ordinal
- 25th
- Roman numeral
- XXV
- Binary
- 11001
- Octal
- 31
- Hexadecimal
- 0x19
- Base64
- GQ==
- One's complement
- 230 (8-bit)
- Scientific notation
- 2.5 × 10¹
As an angle
Historical numeral systems
- Babylonian (base 60)
- 𒌋𒌋𒁹𒁹𒁹𒁹𒁹
- Egyptian hieroglyphic
- 𓎆𓎆𓏺𓏺𓏺𓏺𓏺
- Greek (Milesian)
- κεʹ
- Mayan (base 20)
- 𝋡·𝋥
- Chinese
- 二十五
- Chinese (financial)
- 貳拾伍
Digit at this position in famous constants
- π — Pi (π)
- Digit 25 = 3
- e — Euler's number (e)
- Digit 25 = 7
- φ — Golden ratio (φ)
- Digit 25 = 6
- √2 — Pythagoras's (√2)
- Digit 25 = 8
- ln 2 — Natural log of 2
- Digit 25 = 2
- γ — Euler-Mascheroni (γ)
- Digit 25 = 2
Also seen as
As an ASCII codepoint, 25 is control character (0x19). ASCII control character.
TCP/UDP port 25 is the well-known port for SMTP — Simple Mail Transfer Protocol.
As an unsigned 32-bit integer, this is the IPv4 address 0.0.0.25.
- Address
- 0.0.0.25
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.0.25
Unspecified address (0.0.0.0/8) — "this network" placeholder.
Matches numbered highway designation:
- I-25 — Las Cruces, NM to Buffalo, WY.
Heard as a frequency, 25 Hz is closest to:
- Concert pitch (A4 = 440 Hz): G0 (24.5 Hz, +35¢)
- Scientific pitch (C4 = 256 Hz): G♯0 (25.4 Hz, -27¢)
- Baroque pitch (A4 = 415 Hz): G♯0 (24.5 Hz, +36¢)
As a MIDI note number, 25 is C♯1 (34.6 Hz at concert pitch). (very low — many laptop and phone speakers can't reproduce it)
On the periodic table, atomic number 25 is Manganese (Mn) — period 4.
Related reading
- Egyptian hieroglyphic numerals — Seven hieroglyphs for every power of ten, from a single stroke to a million.