Number
87
- Positive
- Odd
- Composite
- 2 digits
87 is an odd 2-digit integer and a composite number. It has 4 divisors and a digital root of 6.
Number properties
ParityOddnot divisible by 2
SignPositive
PrimalityComposite
Absolute value87
Digit count2
Digit sum15
Digital root6repeated digit sum
PalindromicNoreads differently backwards
Happy numberNosquared-digit sums reach 1
Harshad numberNodivisible by its own digit sum
Factors & divisors
Prime factorisation3 × 29
Distinct prime factors23, 29
Number of divisors4
Sum of divisors σ(n)120
Aliquot sum33sum of the proper divisors
ClassificationDeficientthe aliquot sum is less than the number
Euler's totient φ(n)56integers below n that share no factor with it
SquarefreeYesno repeated prime factor
All divisors1, 3, 29, 874 in total
Arithmetic
Representations
Decimal87
Binary10101117 bits
Octal127
Hexadecimal57
Base 362F
Roman numeralLXXXVII
In wordseighty-seven
Ordinaleighty-seventh
Scientific notation8.7 × 10^1
Engineering notation87
Nearest landmarks
Powers & multiples
87 to the power 27,569
87 to the power 3658,503
87 to the power 457,289,761
87 to the power 54,984,209,207
First ten multiples87, 174, 261, 348, 435, 522, 609, 696, 783, 870
Powers of twoBetween 2^6 (64) and 2^7 (128)
Divisibility tests
Divisible by 2No, remainder 1
Divisible by 3Yes
Divisible by 4No, remainder 3
Divisible by 5No, remainder 2
Divisible by 6No, remainder 3
Divisible by 7No, remainder 3
Divisible by 8No, remainder 7
Divisible by 9No, remainder 6
Divisible by 10No, remainder 7
Divisible by 11No, remainder 10
Divisible by 12No, remainder 3
Divisible by 100No, remainder 87
Collatz (3n + 1) trajectory
Steps to reach 130the total stopping time
Reaches 1Yesthe Collatz conjecture says every positive integer does, but it is unproven
First steps87 → 262 → 131 → 394 → 197 → 592 → 296 → 148 → 74 → 37 → …
Last steps… → 5 → 16 → 8 → 4 → 2 → 1
As a percentage & fraction
As a percentage8,700%
87% as a decimal0.87
87% of 10087
87% of 1,000870
As a fraction of 10087/100
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