The number 81000

Q: Is 81000 a prime number?

No. 81000 = 2^3 × 3^4 × 5^3, so it is divisible by 2.

81000 is a composite number with 80 divisors. Its prime factorisation is $2^{3}$ × $3^{4}$ × $5^{3}$ . Divisors (80): 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 18, 20, 24, 25, 27 … 81000.

Number

Pick any whole number from 1 to 100,000.

81000 = 2^{3} \times 3^{4} \times 5^{3}

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How to work it out

1
What is special about 81000: a Harshad number: divisible by its digit sum 9.
2
81000 is composite. Its prime factorisation is
$81000 = 2^{3} \times 3^{4} \times 5^{3}$
3
The divisors add up to 283140; without 81000 itself that is 202140, so 81000 is abundant (202140 is more than 81000). Euler's totient φ(81000) = 21600 numbers up to 81000 share no factor with it.
4
The digits of 81000 add up to 9, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 45 steps to reach 1.

LaTeX source of the formulas on this page

\[ 81000 = 2^{3} \times 3^{4} \times 5^{3} \]

81000 at a glance

Property	Value
Type	composite
Number of divisors	80
Sum of divisors	283140
Euler totient φ(n)	21600
Square	6561000000
Cube	531441000000000
Square root	284.604989 (= 90√10)
Digit sum / digital root	9 / 9
Collatz steps to 1	45
Scientific notation	8.1 × $10^{4}$

81000 in other forms

Form	Value
In words	eighty-one thousand
Binary (base 2)	10011110001101000
Octal (base 8)	236150
Hexadecimal (base 16)	13C68
Base 3	11010010000
As time	81000 seconds = 22 h 30 min 0 s

Is 81000 divisible by 2 to 12?

Divisor	Answer	Rule
2	Yes (81000 ÷ 2 = 40500)	A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8).
3	Yes (81000 ÷ 3 = 27000)	A number is divisible by 3 if the digits add up to a multiple of 3.
4	Yes (81000 ÷ 4 = 20250)	A number is divisible by 4 if the last two digits make a multiple of 4.
5	Yes (81000 ÷ 5 = 16200)	A number is divisible by 5 if the last digit is 0 or 5.
6	Yes (81000 ÷ 6 = 13500)	A number is divisible by 6 if it is divisible by both 2 and 3.
7	No (remainder 3)	A number is divisible by 7 if double the last digit and subtract it from the rest: the result is a multiple of 7.
8	Yes (81000 ÷ 8 = 10125)	A number is divisible by 8 if the last three digits make a multiple of 8.
9	Yes (81000 ÷ 9 = 9000)	A number is divisible by 9 if the digits add up to a multiple of 9.
10	Yes (81000 ÷ 10 = 8100)	A number is divisible by 10 if the last digit is 0.
11	No (remainder 7)	A number is divisible by 11 if the alternating sum of the digits is a multiple of 11.
12	Yes (81000 ÷ 12 = 6750)	A number is divisible by 12 if it is divisible by both 3 and 4.

Questions

Is 81000 a prime number?

No. 81000 = $2^{3}$ × $3^{4}$ × $5^{3}$ , so it is divisible by 2.

What are the factors of 81000?

1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 18, 20, 24, 25, 27, 30, 36, 40, 45, 50, 54, 60, 72, 75, 81, 90, 100, 108, 120, 125, 135, 150, 162, 180, 200, 216, 225, 250, 270, 300, 324, 360, 375, 405, 450, 500, 540, 600, 648, 675, 750, 810, 900, 1000, 1080, 1125, 1350, 1500, 1620, 1800, 2025, 2250, 2700, 3000, 3240, 3375, 4050, 4500, 5400, 6750, 8100, 9000, 10125, 13500, 16200, 20250, 27000, 40500, 81000.

What is 81000 in binary?

10011110001101000 (hexadecimal 13C68, octal 236150).

What is the square root of 81000?

About 284.6050, exactly 90√10.

Is 81000 divisible by 3?

Yes. Its digits add up to 9, a multiple of 3.

What is special about the number 81000?

81000 is a Harshad number: divisible by its digit sum 9.