Representation numerals

ιηʹ

١٨

XVIII

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十八

חי

Numeral systems

Binary: 10010

Septimal (base 7): 24

Octal: 22

Hexadecimal: 12

Base 24: I

Factorization

18 = 2 × 3 × 3

18 has 6 divisors: 1, 2, 3, 6, 9, 18

Sum of all divisors other than 18: 21

Sums & differences

Sum of 2 squares: 18 = 3^{2} + 3^{2}

Goldbach conjecture: 18 = 13 + 5 = 11 + 7

Characteristics

18 is a heptagonal number