Number
9
- Positive
- Odd
- Composite
- Perfect square
- 1 digit
9 is an odd 1-digit integer and a composite number. It has 3 divisors and a digital root of 9.
Number properties
ParityOddnot divisible by 2
SignPositive
PrimalityComposite
Absolute value9
Digit count1
Digit sum9
Digital root9repeated digit sum
PalindromicYesreads the same backwards
Perfect squareYes, 3²
Happy numberNosquared-digit sums reach 1
Harshad numberYesdivisible by its own digit sum
Armstrong numberYesdigits raised to the digit count sum to itself
Factors & divisors
Prime factorisation3^2
Distinct prime factors13
Number of divisors3
Sum of divisors σ(n)13
Aliquot sum4sum of the proper divisors
ClassificationDeficientthe aliquot sum is less than the number
Euler's totient φ(n)6integers below n that share no factor with it
SquarefreeNohas a repeated prime factor
All divisors1, 3, 93 in total
Arithmetic
Representations
Decimal9
Binary10014 bits
Octal11
Hexadecimal9
Base 369
Roman numeralIX
In wordsnine
Ordinalninth
Scientific notation9 × 10^0
Engineering notation9
Nearest landmarks
Powers & multiples
9 to the power 281
9 to the power 3729
9 to the power 46,561
9 to the power 559,049
First ten multiples9, 18, 27, 36, 45, 54, 63, 72, 81, 90
Powers of twoBetween 2^3 (8) and 2^4 (16)
Divisibility tests
Divisible by 2No, remainder 1
Divisible by 3Yes
Divisible by 4No, remainder 1
Divisible by 5No, remainder 4
Divisible by 6No, remainder 3
Divisible by 7No, remainder 2
Divisible by 8No, remainder 1
Divisible by 9Yes
Divisible by 10No, remainder 9
Divisible by 11No, remainder 9
Divisible by 12No, remainder 9
Divisible by 100No, remainder 9
Collatz (3n + 1) trajectory
Steps to reach 119the total stopping time
Reaches 1Yesthe Collatz conjecture says every positive integer does, but it is unproven
First steps9 → 28 → 14 → 7 → 22 → 11 → 34 → 17 → 52 → 26 → …
Last steps… → 5 → 16 → 8 → 4 → 2 → 1
As a percentage & fraction
As a percentage900%
9% as a decimal0.09
9% of 1009
9% of 1,00090
As a fraction of 1009/100
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Derived from 9
Other readings
Also reads as
U+0039 (unicode character)
- U+0039
- 9
- Decimal digit
U+0039 is code point 57 (9), a decimal digit in the Basic Latin (ASCII) block of the Basic Multilingual Plane. It takes 1 byte in UTF-8 and 1 unit in UTF-16.
Identity
Code pointU+0039
Decimal57
Character9
General categoryDecimal digit
BlockBasic Latin (ASCII)
PlaneBasic Multilingual Planeplane 0
Official nameNot includedthe Unicode Character Database is not bundled; a stale copy would be worse than none
Encodings
UTF-8391 byte
UTF-160039a single unit
UTF-3200000039
Binary111001
Bytes in UTF-8 vs UTF-161 vs 2UTF-16 is not always smaller, even for non-Latin text
Writing it in code
HTML numeric entity9
HTML hex entity9
CSS escape\0039
JavaScript\u0039
Python\u0039
Percent-encoded (URL)%39
Things that catch people out
JavaScript string length1
Needs a surrogate pairNo
Safe in a URL unescapedYes
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