The number 21660

Q: Is 21660 a prime number?

No. 21660 = 2^2 × 3 × 5 × 19^2, so it is divisible by 2.

21660 is a composite number with 36 divisors. Its prime factorisation is $2^{2}$ × 3 × 5 × $19^{2}$ . Divisors (36): 1, 2, 3, 4, 5, 6, 10, 12, 15, 19, 20, 30, 38, 57, 60, 76 … 21660.

Number

Pick any whole number from 1 to 100,000.

21660 = 2^{2} \times 3 \times 5 \times 19^{2}

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How to work it out

1
What is special about 21660: a Harshad number: divisible by its digit sum 15.
2
21660 is composite. Its prime factorisation is
$21660 = 2^{2} \times 3 \times 5 \times 19^{2}$
3
The divisors add up to 64008; without 21660 itself that is 42348, so 21660 is abundant (42348 is more than 21660). Euler's totient φ(21660) = 5472 numbers up to 21660 share no factor with it.
4
The digits of 21660 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 43 steps to reach 1.

LaTeX source of the formulas on this page

\[ 21660 = 2^{2} \times 3 \times 5 \times 19^{2} \]

21660 at a glance

Property	Value
Type	composite
Number of divisors	36
Sum of divisors	64008
Euler totient φ(n)	5472
Square	469155600
Cube	10161910296000
Square root	147.173367 (= 38√15)
Digit sum / digital root	15 / 6
Collatz steps to 1	43
Scientific notation	2.166 × $10^{4}$

21660 in other forms

Form	Value
In words	twenty-one thousand six hundred and sixty
Binary (base 2)	101010010011100
Octal (base 8)	52234
Hexadecimal (base 16)	549C
Base 3	1002201020
As time	21660 seconds = 6 h 1 min 0 s

Is 21660 divisible by 2 to 12?

Divisor	Answer	Rule
2	Yes (21660 ÷ 2 = 10830)	A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8).
3	Yes (21660 ÷ 3 = 7220)	A number is divisible by 3 if the digits add up to a multiple of 3.
4	Yes (21660 ÷ 4 = 5415)	A number is divisible by 4 if the last two digits make a multiple of 4.
5	Yes (21660 ÷ 5 = 4332)	A number is divisible by 5 if the last digit is 0 or 5.
6	Yes (21660 ÷ 6 = 3610)	A number is divisible by 6 if it is divisible by both 2 and 3.
7	No (remainder 2)	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 (21660 ÷ 10 = 2166)	A number is divisible by 10 if the last digit is 0.
11	No (remainder 1)	A number is divisible by 11 if the alternating sum of the digits is a multiple of 11.
12	Yes (21660 ÷ 12 = 1805)	A number is divisible by 12 if it is divisible by both 3 and 4.

Questions

Is 21660 a prime number?

No. 21660 = $2^{2}$ × 3 × 5 × $19^{2}$ , so it is divisible by 2.

What are the factors of 21660?

1, 2, 3, 4, 5, 6, 10, 12, 15, 19, 20, 30, 38, 57, 60, 76, 95, 114, 190, 228, 285, 361, 380, 570, 722, 1083, 1140, 1444, 1805, 2166, 3610, 4332, 5415, 7220, 10830, 21660.

What is 21660 in binary?

101010010011100 (hexadecimal 549C, octal 52234).

What is the square root of 21660?

About 147.1734, exactly 38√15.

Is 21660 divisible by 3?

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

What is special about the number 21660?

21660 is a Harshad number: divisible by its digit sum 15.