28 ( twenty eight ) is a natural number located between the numbers 27 and 29 .
| 28 | |
|---|---|
| twenty eight | |
| ← 26 · 27 · 28 · 29 · 30 → | |
| Factorization | 2 2 7 |
| Roman notation | Xxviii |
| Binary | 11100 |
| Octal | 34 |
| Hexadecimal | 1C |
Content
Math
- Even two-digit number
- Odious number
- Whale number
- The second perfect number . ↓ 6 , ↑ 496
- Seventh triangular number . ↓ 21 , ↑ 36
- The fourth hexagonal number . ↓ 15 , ↑ 45
- The sum of the first five primes : 28 = 2 + 3 + 5 + 7 + 11. ↓ 17 , ↑ 41
- The sum of the first five difficult numbers: 28 = 1 + 4 + 6 + 8 + 9
- There are 28 match graphs with 6 edges [1] .
Science
- Atomic number of nickel .
- One of the twice magic occupation numbers (that is, magic for both protons and neutrons) in the shell model of the nucleus (similar to the theory of the shell structure of an atom ). Isotopes with 28 protons or 28 neutrons are characterized by increased stability (the binding energy of the next nucleon is much less than the last).
- Approximately 28 days (29 d 12 h 44.0 min, sidereal period - 27 d 7 h 43.1 min) is the lunar month ( synodic period of revolution of the moon , time of repetition of the lunar phases). See also Menstrual cycle .
- 10 to 28 degrees cm - the size of the visible part of the universe.
- The space station Mir carried out 28 long-term expeditions.
Calendar
- Numbers associated with the Gregorian calendar : 4 , 7 , 14 , 28 , 29 , 30 , 31 , 52 , 90 , 91 , 92 , 97 , 100 , 365 , 366 , 400
- The number of days in February of a non-leap year. Initially, there were 30 days in February, but then added the 31st day to July in honor of Julius Caesar and the 31st day to August in honor of Octavian Augustus , respectively removing 2 days from February.
- The Julian calendar repeats every 28 years.
In other areas
- 28 states in the European Union .
- ASCII code for the
FScontrol character (file separator) - 28 - Code of the subject of the Russian Federation of the Amur Region
- The 28th letter of the Russian alphabet is Kommersant .
- The number of letters in the Arabic alphabet and in the Esperanto alphabet.
- In the Soviet Union there were only 28 congresses of the Central Committee of the CPSU .
- 28 years - the age of exit from the Komsomol for ordinary Komsomol members in the USSR.
- The number of bones in a standard set of dominoes
- 28 Panfilov heroes.
- 28 pages - the final part of the parliamentary investigation of the September 11 attacks, which states that these attacks were organized by Saudi Arabia.
- At 28 weeks of gestation, the baby usually opens its eyes.
- 28 is the code for the neo-Nazi music promotion network Blood and Honor , in which “2” means “B” (the second letter of the alphabet) and “8” means “H” (the eighth letter of the alphabet). This explains the prohibition on the use of the number 28 imposed by UEFA .
- Number 28 by month: January 28 | February 28th | March 28th | April 28th | May 28 | June 28th | July 28th | August 28th | September 28th | October 28th | November 28th | December 28th
- Federal Law No. 28 (On Fake News)
Cinema
- 28 weeks later
- 28 days later
- Twenty-Eight Panfilovites (film)
Notes
- ↑ Sequence A066951 in OEIS = Number of nonisomorphic connected graphs that can be drawn in the plane using n unit-length edges // Fragment: 1, 1 , 3 , 5 , 12 , 28 , 74 , 207, 633 , 2008