The number 20840
20840 is a composite number with 16 divisors. Its prime factorisation is × 5 × 521. Divisors (16): 1, 2, 4, 5, 8, 10, 20, 40, 521, 1042, 2084, 2605, 4168, 5210, 10420, 20840.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
20840 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
20840 is composite. Its prime factorisation is
- 3
The divisors add up to 46980; without 20840 itself that is 26140, so 20840 is abundant (26140 is more than 20840). Euler's totient φ(20840) = 8320 numbers up to 20840 share no factor with it.
- 4
The digits of 20840 add up to 14, and repeating that until one digit is left gives the digital root 5. The Collatz sequence (halve if even, else 3n+1) takes 105 steps to reach 1.
LaTeX source of the formulas on this page
\[ 20840 = 2^{3} \times 5 \times 521 \]20840 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 46980 |
| Euler totient φ(n) | 8320 |
| Square | 434305600 |
| Cube | 9050928704000 |
| Square root | 144.360659 (= 2√5210) |
| Digit sum / digital root | 14 / 5 |
| Collatz steps to 1 | 105 |
| Scientific notation | 2.084 × |
20840 in other forms
| Form | Value |
|---|---|
| In words | twenty thousand eight hundred and forty |
| Binary (base 2) | 101000101101000 |
| Octal (base 8) | 50550 |
| Hexadecimal (base 16) | 5168 |
| Base 3 | 1001120212 |
| As time | 20840 seconds = 5 h 47 min 20 s |
Is 20840 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (20840 ÷ 2 = 10420) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | No (remainder 2) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (20840 ÷ 4 = 5210) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (20840 ÷ 5 = 4168) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 2) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 1) | 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 (20840 ÷ 8 = 2605) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 5) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (20840 ÷ 10 = 2084) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 6) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 8) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 20840 a prime number?
No. 20840 = × 5 × 521, so it is divisible by 2.
What are the factors of 20840?
1, 2, 4, 5, 8, 10, 20, 40, 521, 1042, 2084, 2605, 4168, 5210, 10420, 20840.
What is 20840 in binary?
101000101101000 (hexadecimal 5168, octal 50550).
What is the square root of 20840?
About 144.3607, exactly 2√5210.
Is 20840 divisible by 3?
No. Its digits add up to 14, which is not a multiple of 3.
What is special about the number 20840?
It is a composite number with 16 divisors.