Recognised as Number
-18
- Negative
- Even
- 2 digits
-18 is an even 2-digit integer and the negative of 18. It has 6 divisors and a digital root of 9.
Number properties
ParityEvendivisible by 2
SignNegative
Absolute value18
Digit count2
Digit sum9
Digit product8
Multiplicative persistence1times the digit product can be taken before one digit is left
Digital root9repeated digit sum
PalindromicNoreads differently backwards
Factors & divisors
Prime factorisation−1 × 2 × 3^2
Distinct prime factors22, 3
Number of divisors6
Sum of divisors σ(n)39
SquarefreeNohas a repeated prime factor
All divisors1, 2, 3, 6, 9, 186 in total
Arithmetic
Representations
Decimal-18
Binary100105 bits
Octal22
Hexadecimal12
Base 36I
In wordsminus eighteen
Ordinalminus eighteenth
Scientific notation-1.8 × 10^1
Engineering notation-18
In other bases
Ternary200base 3; the most digit-efficient integer base after e: 3 digits
Quinary33base 5; one hand: 2 digits
Septenary24base 7: 2 digits
Nonary20base 9; each digit is two ternary digits: 2 digits
Duodecimal16base 12; divides by 2, 3, 4 and 6, which is why eggs and inches come in twelves: 2 digits
Vigesimalibase 20; hands and feet, and the Mayan and Yoruba systems: 1 digit
Sexagesimal18base 60; Babylonian, and still how an hour and a circle are divided: 1 digit
Balanced ternaryT100digits −1, 0 and +1 written T, 0 and 1; negation is swapping T and 1, so no sign is needed
Negabinary110010base −2; place values alternate 1, −2, 4, −8, so every integer has exactly one form without a sign
Bit-level
11101110
Bit length5 bitsto write the magnitude
Set bits2the population count, or Hamming weight
Zero bits3within that length
Bit parityeven2 set bits, so even; not the same as the number itself being even
Highest set bitbit 4worth 16
Lowest set bitbit 11 trailing zero
Power of twoNo
Bytes112
Gray code11011n XOR (n >> 1); successive values differ in exactly one bit
At each machine width
8-bit11101110two's complement
16-bit1111111111101110two's complement
32-bit11111111111111111111111111101110two's complement
64-bit1111111111111111111111111111111111111111111111111111111111101110two's complement
One's complement00010001at 8 bits, every bit flipped
Bits reversed01110111at 8 bits
Rotated left by 111011101at 8 bits, wrapping
Shifted left by 1-100100= -36, no wrap
Shifted right by 1-1001= -9, discarding the low bit
These bits as a double8.89318163 × 10^-323≈IEEE-754 binary64 reinterpretation of the same 64 bits (subnormal)
Powers & multiples
-18 to the power 2324
-18 to the power 3-5,832
-18 to the power 4104,976
-18 to the power 5-1,889,568
First ten multiples-18, -36, -54, -72, -90, -108, -126, -144, -162, -180
Powers of twoBetween 2^4 (16) and 2^5 (32)
Divisibility tests
Divisible by 2Yes
Divisible by 3Yes
Divisible by 4No, remainder 2
Divisible by 5No, remainder 3
Divisible by 6Yes
Divisible by 7No, remainder 4
Divisible by 8No, remainder 2
Divisible by 9Yes
Divisible by 10No, remainder 8
Divisible by 11No, remainder 7
Divisible by 12No, remainder 6
Divisible by 100No, remainder 18
As a percentage & fraction
As a percentage-1,800%
-18% as a decimal-0.18
-18% of 100-18
-18% of 1,000-180
As a fraction of 100-18/100
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