Number
90
- Positive
- Even
- Composite
- 2 digits
90 is an even 2-digit integer and a composite number. It has 12 divisors and a digital root of 9.
Number properties
ParityEvendivisible by 2
SignPositive
PrimalityComposite
Absolute value90
Digit count2
Digit sum9
Digital root9repeated digit sum
PalindromicNoreads differently backwards
Happy numberNosquared-digit sums reach 1
Harshad numberYesdivisible by its own digit sum
Factors & divisors
Prime factorisation2 × 3^2 × 5
Distinct prime factors32, 3, 5
Number of divisors12
Sum of divisors σ(n)234
Aliquot sum144sum of the proper divisors
ClassificationAbundantthe aliquot sum exceeds the number
Euler's totient φ(n)24integers below n that share no factor with it
SquarefreeNohas a repeated prime factor
All divisors1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, 9012 in total
Arithmetic
Representations
Decimal90
Binary10110107 bits
Octal132
Hexadecimal5A
Base 362I
Roman numeralXC
In wordsninety
Ordinalninetieth
Scientific notation9 × 10^1
Engineering notation90
Nearest landmarks
Powers & multiples
90 to the power 28,100
90 to the power 3729,000
90 to the power 465,610,000
90 to the power 55,904,900,000
First ten multiples90, 180, 270, 360, 450, 540, 630, 720, 810, 900
Powers of twoBetween 2^6 (64) and 2^7 (128)
Divisibility tests
Divisible by 2Yes
Divisible by 3Yes
Divisible by 4No, remainder 2
Divisible by 5Yes
Divisible by 6Yes
Divisible by 7No, remainder 6
Divisible by 8No, remainder 2
Divisible by 9Yes
Divisible by 10Yes
Divisible by 11No, remainder 2
Divisible by 12No, remainder 6
Divisible by 100No, remainder 90
Collatz (3n + 1) trajectory
Steps to reach 117the total stopping time
Reaches 1Yesthe Collatz conjecture says every positive integer does, but it is unproven
First steps90 → 45 → 136 → 68 → 34 → 17 → 52 → 26 → 13 → 40 → …
Last steps… → 5 → 16 → 8 → 4 → 2 → 1
As a percentage & fraction
As a percentage9,000%
90% as a decimal0.9
90% of 10090
90% of 1,000900
As a fraction of 10090/100
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