The number 21640
21640 is a composite number with 16 divisors. Its prime factorisation is × 5 × 541. Divisors (16): 1, 2, 4, 5, 8, 10, 20, 40, 541, 1082, 2164, 2705, 4328, 5410, 10820, 21640.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21640 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21640 is composite. Its prime factorisation is
- 3
The divisors add up to 48780; without 21640 itself that is 27140, so 21640 is abundant (27140 is more than 21640). Euler's totient φ(21640) = 8640 numbers up to 21640 share no factor with it.
- 4
The digits of 21640 add up to 13, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 43 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21640 = 2^{3} \times 5 \times 541 \]21640 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 48780 |
| Euler totient φ(n) | 8640 |
| Square | 468289600 |
| Cube | 10133786944000 |
| Square root | 147.105404 (= 2√5410) |
| Digit sum / digital root | 13 / 4 |
| Collatz steps to 1 | 43 |
| Scientific notation | 2.164 × |
21640 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand six hundred and forty |
| Binary (base 2) | 101010010001000 |
| Octal (base 8) | 52210 |
| Hexadecimal (base 16) | 5488 |
| Base 3 | 1002200111 |
| As time | 21640 seconds = 6 h 0 min 40 s |
Is 21640 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21640 ÷ 2 = 10820) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | No (remainder 1) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (21640 ÷ 4 = 5410) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (21640 ÷ 5 = 4328) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 4) | 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 (21640 ÷ 8 = 2705) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 4) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (21640 ÷ 10 = 2164) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 3) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 4) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21640 a prime number?
No. 21640 = × 5 × 541, so it is divisible by 2.
What are the factors of 21640?
1, 2, 4, 5, 8, 10, 20, 40, 541, 1082, 2164, 2705, 4328, 5410, 10820, 21640.
What is 21640 in binary?
101010010001000 (hexadecimal 5488, octal 52210).
What is the square root of 21640?
About 147.1054, exactly 2√5410.
Is 21640 divisible by 3?
No. Its digits add up to 13, which is not a multiple of 3.
What is special about the number 21640?
It is a composite number with 16 divisors.