The number 21540
21540 is a composite number with 24 divisors. Its prime factorisation is × 3 × 5 × 359. Divisors (24): 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60, 359, 718, 1077, 1436 … 21540.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21540: a Harshad number: divisible by its digit sum 12.
- 2
21540 is composite. Its prime factorisation is
- 3
The divisors add up to 60480; without 21540 itself that is 38940, so 21540 is abundant (38940 is more than 21540). Euler's totient φ(21540) = 5728 numbers up to 21540 share no factor with it.
- 4
The digits of 21540 add up to 12, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 149 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21540 = 2^{2} \times 3 \times 5 \times 359 \]21540 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 60480 |
| Euler totient φ(n) | 5728 |
| Square | 463971600 |
| Cube | 9993948264000 |
| Square root | 146.765118 (= 2√5385) |
| Digit sum / digital root | 12 / 3 |
| Collatz steps to 1 | 149 |
| Scientific notation | 2.154 × |
21540 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand five hundred and forty |
| Binary (base 2) | 101010000100100 |
| Octal (base 8) | 52044 |
| Hexadecimal (base 16) | 5424 |
| Base 3 | 1002112210 |
| As time | 21540 seconds = 5 h 59 min 0 s |
Is 21540 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21540 ÷ 2 = 10770) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21540 ÷ 3 = 7180) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (21540 ÷ 4 = 5385) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (21540 ÷ 5 = 4308) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | Yes (21540 ÷ 6 = 3590) | 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 | No (remainder 4) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 3) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (21540 ÷ 10 = 2154) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 2) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | Yes (21540 ÷ 12 = 1795) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21540 a prime number?
No. 21540 = × 3 × 5 × 359, so it is divisible by 2.
What are the factors of 21540?
1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60, 359, 718, 1077, 1436, 1795, 2154, 3590, 4308, 5385, 7180, 10770, 21540.
What is 21540 in binary?
101010000100100 (hexadecimal 5424, octal 52044).
What is the square root of 21540?
About 146.7651, exactly 2√5385.
Is 21540 divisible by 3?
Yes. Its digits add up to 12, a multiple of 3.
What is special about the number 21540?
21540 is a Harshad number: divisible by its digit sum 12.