Representation numerals

κηʹ

٢٨

XXVIII

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二十八

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 = 8^{2} - 6^{2}

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)

(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

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The next triangular is: 36

28 is a hexagonal number