Number
20
- Positive
- Even
- Composite
- 2 digits
20 is an even 2-digit integer and a composite number. It has 6 divisors and a digital root of 2.
Number properties
ParityEvendivisible by 2
SignPositive
PrimalityComposite
Absolute value20
Digit count2
Digit sum2
Digital root2repeated digit sum
PalindromicNoreads differently backwards
Happy numberNosquared-digit sums reach 1
Harshad numberYesdivisible by its own digit sum
Factors & divisors
Prime factorisation2^2 × 5
Distinct prime factors22, 5
Number of divisors6
Sum of divisors σ(n)42
Aliquot sum22sum of the proper divisors
ClassificationAbundantthe aliquot sum exceeds the number
Euler's totient φ(n)8integers below n that share no factor with it
SquarefreeNohas a repeated prime factor
All divisors1, 2, 4, 5, 10, 206 in total
Arithmetic
Representations
Decimal20
Binary101005 bits
Octal24
Hexadecimal14
Base 36K
Roman numeralXX
In wordstwenty
Ordinaltwentieth
Scientific notation2 × 10^1
Engineering notation20
Nearest landmarks
Powers & multiples
20 to the power 2400
20 to the power 38,000
20 to the power 4160,000
20 to the power 53,200,000
First ten multiples20, 40, 60, 80, 100, 120, 140, 160, 180, 200
Powers of twoBetween 2^4 (16) and 2^5 (32)
Divisibility tests
Divisible by 2Yes
Divisible by 3No, remainder 2
Divisible by 4Yes
Divisible by 5Yes
Divisible by 6No, remainder 2
Divisible by 7No, remainder 6
Divisible by 8No, remainder 4
Divisible by 9No, remainder 2
Divisible by 10Yes
Divisible by 11No, remainder 9
Divisible by 12No, remainder 8
Divisible by 100No, remainder 20
Collatz (3n + 1) trajectory
Steps to reach 17the total stopping time
Highest value reached20
Reaches 1Yesthe Collatz conjecture says every positive integer does, but it is unproven
First steps20 → 10 → 5 → 16 → 8 → 4 → 2 → 1
As a percentage & fraction
As a percentage2,000%
20% as a decimal0.2
20% of 10020
20% of 1,000200
As a fraction of 10020/100
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