18
Everything about the number 18 — its names, how to write it in other bases and numeral systems, and what makes it interesting mathematically.
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Names of 18
| Nominal | 18 |
| Cardinal | eighteen |
| Ordinal | 18th |
| This number as US currency | eighteen dollars |
Properties (and some facts) of 18
| Is 18 an odd number? | 18 is not an odd number |
| Is 18 an even number? | 18 is an even number |
| Is 18 a palindrome? | 18 is not a palindrome |
| Is 18 a triangle number? | 18 is not a triangle number |
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18 in other bases
| Base 2 (Binary) | 10010 |
| Base 3 (Ternary) | 200 |
| Base 4 (Quaternary) | 102 |
| Base 5 (Quinary) | 33 |
| Base 6 (Senary) | 30 |
| Base 8 (Octal) | 22 |
| Base 12 (Duodecimal) | 16 |
| Base 16 (Hexadecimal) | 12 |
| Base 20 (Vigesimal) | I |
Primes and factors tests for 18
| Is 18 a prime number? | 18 is not a prime number |
| Is 18 a perfect number? | 18 is not a perfect number |
| Is 18 a Mersenne prime? | 18 is not a Mersenne prime |
| Is 18 a Fermat prime? | 18 is not a Fermat prime |
| Is 18 a Fibonacci prime? | 18 is not a Fibonacci prime |
| Is 18 a partition prime? | 18 is not a partition prime |
| Is 18 a Pell prime? | 18 is not a Pell prime |
| Prime Factors | Prime factors of 18 |
18 in other numeral systems
| 18 in Roman numerals | XVIII |
| 18 in Chinese numerals | 壹拾捌 |
| 18 in Babylonian numerals |  |
| 18 in Egyptian numerals | 𓎆𓐁 |
Roots and squares for 18
| Is 18 a square number? | 18 is not a square number |
| Is 18 a cube number? | 18 is not a cube number |
| Square root of 18 | 4.2426406871193 |
| Cube root of 18 | 2.6207413942089 |
Recreational math for 18
| Number 18 reversed | 81 |
| Sum of the digits | 9 |
| Number of digits | 2 |
Arithmetic tables for 18
Other pages about 18
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