The number 21920
21920 is a composite number with 24 divisors. Its prime factorisation is × 5 × 137. Divisors (24): 1, 2, 4, 5, 8, 10, 16, 20, 32, 40, 80, 137, 160, 274, 548, 685 … 21920.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21920 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21920 is composite. Its prime factorisation is
- 3
The divisors add up to 52164; without 21920 itself that is 30244, so 21920 is abundant (30244 is more than 21920). Euler's totient φ(21920) = 8704 numbers up to 21920 share no factor with it.
- 4
The digits of 21920 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 131 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21920 = 2^{5} \times 5 \times 137 \]21920 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 52164 |
| Euler totient φ(n) | 8704 |
| Square | 480486400 |
| Cube | 10532261888000 |
| Square root | 148.054044 (= 4√1370) |
| Digit sum / digital root | 14 / 5 |
| Collatz steps to 1 | 131 |
| Scientific notation | 2.192 × |
21920 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand nine hundred and twenty |
| Binary (base 2) | 101010110100000 |
| Octal (base 8) | 52640 |
| Hexadecimal (base 16) | 55A0 |
| Base 3 | 1010001212 |
| As time | 21920 seconds = 6 h 5 min 20 s |
Is 21920 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21920 ÷ 2 = 10960) | 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 (21920 ÷ 4 = 5480) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (21920 ÷ 5 = 4384) | 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 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 (21920 ÷ 8 = 2740) | 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 (21920 ÷ 10 = 2192) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 8) | 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 21920 a prime number?
No. 21920 = × 5 × 137, so it is divisible by 2.
What are the factors of 21920?
1, 2, 4, 5, 8, 10, 16, 20, 32, 40, 80, 137, 160, 274, 548, 685, 1096, 1370, 2192, 2740, 4384, 5480, 10960, 21920.
What is 21920 in binary?
101010110100000 (hexadecimal 55A0, octal 52640).
What is the square root of 21920?
About 148.0540, exactly 4√1370.
Is 21920 divisible by 3?
No. Its digits add up to 14, which is not a multiple of 3.
What is special about the number 21920?
It is a composite number with 24 divisors.