28 (number)
Natural number
From Wikipedia, the free encyclopedia
28 (twenty-eight) is the natural number following 27 and preceding 29.
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| ||||
|---|---|---|---|---|
| Cardinal | twenty-eight | |||
| Ordinal | 28th (twenty-eighth) | |||
| Factorization | 22 × 7 | |||
| Divisors | 1, 2, 4, 7, 14, 28 | |||
| Greek numeral | ΚΗ´ | |||
| Roman numeral | XXVIII, xxviii | |||
| Binary | 111002 | |||
| Ternary | 10013 | |||
| Senary | 446 | |||
| Octal | 348 | |||
| Duodecimal | 2412 | |||
| Hexadecimal | 1C16 | |||
28 is a composite number, a perfect number,[1] a harmonic divisor number,[2] a centered nonagonal number,[3] a hexagonal number,[4] a happy number,[5] and a triangular number.[6]
28 also appears in the Padovan sequence.[7]
In algebraic geometry, 28 is the number of bitangents to a general plane quartic curve.
In science
28 is the fourth magic number in physics. It is also the atomic number of the element Nickel.