Number
13
- Positive
- Odd
- Prime
- 2 digits
13 is an odd 2-digit integer and a prime number. It has 2 divisors and a digital root of 4.
Number properties
ParityOddnot divisible by 2
SignPositive
PrimalityPrime
Absolute value13
Digit count2
Digit sum4
Digital root4repeated digit sum
PalindromicNoreads differently backwards
Fibonacci numberYes, F(7)
Happy numberYessquared-digit sums reach 1
Harshad numberNodivisible by its own digit sum
Factors & divisors
Prime factorisation13
Distinct prime factors113
Number of divisors2
Sum of divisors σ(n)14
Aliquot sum1sum of the proper divisors
ClassificationDeficientthe aliquot sum is less than the number
Euler's totient φ(n)12integers below n that share no factor with it
SquarefreeYesno repeated prime factor
All divisors1, 132 in total
Arithmetic
Representations
Decimal13
Binary11014 bits
Octal15
HexadecimalD
Base 36D
Roman numeralXIII
In wordsthirteen
Ordinalthirteenth
Scientific notation1.3 × 10^1
Engineering notation13
Nearest landmarks
Powers & multiples
13 to the power 2169
13 to the power 32,197
13 to the power 428,561
13 to the power 5371,293
First ten multiples13, 26, 39, 52, 65, 78, 91, 104, 117, 130
Powers of twoBetween 2^3 (8) and 2^4 (16)
Divisibility tests
Divisible by 2No, remainder 1
Divisible by 3No, remainder 1
Divisible by 4No, remainder 1
Divisible by 5No, remainder 3
Divisible by 6No, remainder 1
Divisible by 7No, remainder 6
Divisible by 8No, remainder 5
Divisible by 9No, remainder 4
Divisible by 10No, remainder 3
Divisible by 11No, remainder 2
Divisible by 12No, remainder 1
Divisible by 100No, remainder 13
Collatz (3n + 1) trajectory
Steps to reach 19the total stopping time
Reaches 1Yesthe Collatz conjecture says every positive integer does, but it is unproven
First steps13 → 40 → 20 → 10 → 5 → 16 → 8 → 4 → 2 → 1
As a percentage & fraction
As a percentage1,300%
13% as a decimal0.13
13% of 10013
13% of 1,000130
As a fraction of 10013/100
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