The number 21520
21520 is a composite number with 20 divisors. Its prime factorisation is × 5 × 269. Divisors (20): 1, 2, 4, 5, 8, 10, 16, 20, 40, 80, 269, 538, 1076, 1345, 2152, 2690 … 21520.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21520: a Harshad number: divisible by its digit sum 10.
- 2
21520 is composite. Its prime factorisation is
- 3
The divisors add up to 50220; without 21520 itself that is 28700, so 21520 is abundant (28700 is more than 21520). Euler's totient φ(21520) = 8576 numbers up to 21520 share no factor with it.
- 4
The digits of 21520 add up to 10, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 118 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21520 = 2^{4} \times 5 \times 269 \]21520 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 20 |
| Sum of divisors | 50220 |
| Euler totient φ(n) | 8576 |
| Square | 463110400 |
| Cube | 9966135808000 |
| Square root | 146.696967 (= 4√1345) |
| Digit sum / digital root | 10 / 1 |
| Collatz steps to 1 | 118 |
| Scientific notation | 2.152 × |
21520 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand five hundred and twenty |
| Binary (base 2) | 101010000010000 |
| Octal (base 8) | 52020 |
| Hexadecimal (base 16) | 5410 |
| Base 3 | 1002112001 |
| As time | 21520 seconds = 5 h 58 min 40 s |
Is 21520 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21520 ÷ 2 = 10760) | 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 (21520 ÷ 4 = 5380) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (21520 ÷ 5 = 4304) | 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 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 | Yes (21520 ÷ 8 = 2690) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 1) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (21520 ÷ 10 = 2152) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 4) | 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 21520 a prime number?
No. 21520 = × 5 × 269, so it is divisible by 2.
What are the factors of 21520?
1, 2, 4, 5, 8, 10, 16, 20, 40, 80, 269, 538, 1076, 1345, 2152, 2690, 4304, 5380, 10760, 21520.
What is 21520 in binary?
101010000010000 (hexadecimal 5410, octal 52020).
What is the square root of 21520?
About 146.6970, exactly 4√1345.
Is 21520 divisible by 3?
No. Its digits add up to 10, which is not a multiple of 3.
What is special about the number 21520?
21520 is a Harshad number: divisible by its digit sum 10.