The number 28

Representation numerals

Greek numeral

κηʹ

Arabic numeral

٢٨

Roman numeral

XXVIII

Maya numeral


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Chinese numeral

二十八

Hebrew numeral

כח
Numeral systems
Binary: 11100
Septimal (base 7): 40
Octal: 34
Hexadecimal: 1c
Base 24: 14
Factorization
28 = 2 × 2 × 7
28 has 6 divisors: 1, 2, 4, 7, 14, 28
Sum of all divisors other than 28: 28
Sums & differences
28 is the sum of the first 5 prime numbers: 28 = 2 + 3 + 5 + 7 + 11
Difference of 2 squares: 28 = 82 - 62
Goldbach conjecture: 28 = 23 + 5 = 17 + 11
Characteristics
28 is a perfect number
(a number is perfect if it’s equal to the sum of its divisors other than itself)
28 is a triangular number

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The next triangular is: 36
28 is a hexagonal number
Related primes
The 28th prime number is: 107
Previous prime number: 23 — Next prime number: 29
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