The number 81420

Q: Is 81420 a prime number?

No. 81420 = 2^2 × 3 × 5 × 23 × 59, so it is divisible by 2.

81420 is a composite number with 48 divisors. Its prime factorisation is $2^{2}$ × 3 × 5 × 23 × 59. Divisors (48): 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 23, 30, 46, 59, 60, 69 … 81420.

Number

Pick any whole number from 1 to 100,000.

81420 = 2^{2} \times 3 \times 5 \times 23 \times 59

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How to work it out

1
What is special about 81420: a Harshad number: divisible by its digit sum 15.
2
81420 is composite. Its prime factorisation is
$81420 = 2^{2} \times 3 \times 5 \times 23 \times 59$
3
The divisors add up to 241920; without 81420 itself that is 160500, so 81420 is abundant (160500 is more than 81420). Euler's totient φ(81420) = 20416 numbers up to 81420 share no factor with it.
4
The digits of 81420 add up to 15, and repeating that until one digit is left gives the digital root 6. The Collatz sequence (halve if even, else 3n+1) takes 37 steps to reach 1.

LaTeX source of the formulas on this page

\[ 81420 = 2^{2} \times 3 \times 5 \times 23 \times 59 \]

81420 at a glance

Property	Value
Type	composite
Number of divisors	48
Sum of divisors	241920
Euler totient φ(n)	20416
Square	6629216400
Cube	539750799288000
Square root	285.341900 (= 2√20355)
Digit sum / digital root	15 / 6
Collatz steps to 1	37
Scientific notation	8.142 × $10^{4}$

81420 in other forms

Form	Value
In words	eighty-one thousand four hundred and twenty
Binary (base 2)	10011111000001100
Octal (base 8)	237014
Hexadecimal (base 16)	13E0C
Base 3	11010200120
As time	81420 seconds = 22 h 37 min 0 s

Is 81420 divisible by 2 to 12?

Divisor	Answer	Rule
2	Yes (81420 ÷ 2 = 40710)	A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8).
3	Yes (81420 ÷ 3 = 27140)	A number is divisible by 3 if the digits add up to a multiple of 3.
4	Yes (81420 ÷ 4 = 20355)	A number is divisible by 4 if the last two digits make a multiple of 4.
5	Yes (81420 ÷ 5 = 16284)	A number is divisible by 5 if the last digit is 0 or 5.
6	Yes (81420 ÷ 6 = 13570)	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	No (remainder 4)	A number is divisible by 8 if the last three digits make a multiple of 8.
9	No (remainder 6)	A number is divisible by 9 if the digits add up to a multiple of 9.
10	Yes (81420 ÷ 10 = 8142)	A number is divisible by 10 if the last digit is 0.
11	No (remainder 9)	A number is divisible by 11 if the alternating sum of the digits is a multiple of 11.
12	Yes (81420 ÷ 12 = 6785)	A number is divisible by 12 if it is divisible by both 3 and 4.

Questions

Is 81420 a prime number?

No. 81420 = $2^{2}$ × 3 × 5 × 23 × 59, so it is divisible by 2.

What are the factors of 81420?

1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 23, 30, 46, 59, 60, 69, 92, 115, 118, 138, 177, 230, 236, 276, 295, 345, 354, 460, 590, 690, 708, 885, 1180, 1357, 1380, 1770, 2714, 3540, 4071, 5428, 6785, 8142, 13570, 16284, 20355, 27140, 40710, 81420.

What is 81420 in binary?

10011111000001100 (hexadecimal 13E0C, octal 237014).

What is the square root of 81420?

About 285.3419, exactly 2√20355.

Is 81420 divisible by 3?

Yes. Its digits add up to 15, a multiple of 3.

What is special about the number 81420?

81420 is a Harshad number: divisible by its digit sum 15.