The number 21690
21690 is a composite number with 24 divisors. Its prime factorisation is 2 × × 5 × 241. Divisors (24): 1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, 90, 241, 482, 723, 1205 … 21690.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21690: a Harshad number: divisible by its digit sum 18.
- 2
21690 is composite. Its prime factorisation is
- 3
The divisors add up to 56628; without 21690 itself that is 34938, so 21690 is abundant (34938 is more than 21690). Euler's totient φ(21690) = 5760 numbers up to 21690 share no factor with it.
- 4
The digits of 21690 add up to 18, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 118 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21690 = 2 \times 3^{2} \times 5 \times 241 \]21690 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 56628 |
| Euler totient φ(n) | 5760 |
| Square | 470456100 |
| Cube | 10204192809000 |
| Square root | 147.275253 (= 3√2410) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 118 |
| Scientific notation | 2.169 × |
21690 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand six hundred and ninety |
| Binary (base 2) | 101010010111010 |
| Octal (base 8) | 52272 |
| Hexadecimal (base 16) | 54BA |
| Base 3 | 1002202100 |
| As time | 21690 seconds = 6 h 1 min 30 s |
Is 21690 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21690 ÷ 2 = 10845) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21690 ÷ 3 = 7230) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 2) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (21690 ÷ 5 = 4338) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | Yes (21690 ÷ 6 = 3615) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 4) | 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 2) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (21690 ÷ 9 = 2410) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (21690 ÷ 10 = 2169) | 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 | No (remainder 6) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21690 a prime number?
No. 21690 = 2 × × 5 × 241, so it is divisible by 2.
What are the factors of 21690?
1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, 90, 241, 482, 723, 1205, 1446, 2169, 2410, 3615, 4338, 7230, 10845, 21690.
What is 21690 in binary?
101010010111010 (hexadecimal 54BA, octal 52272).
What is the square root of 21690?
About 147.2753, exactly 3√2410.
Is 21690 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 21690?
21690 is a Harshad number: divisible by its digit sum 18.