The number 21528
21528 is a triangular number: 1 + 2 + … + 207 = 21528. Its prime factorisation is × × 13 × 23. Divisors (48): 1, 2, 3, 4, 6, 8, 9, 12, 13, 18, 23, 24, 26, 36, 39, 46 … 21528.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21528: a triangular number: 1 + 2 + … + 207 = 21528; a Harshad number: divisible by its digit sum 18.
- 2
21528 is composite. Its prime factorisation is
- 3
The divisors add up to 65520; without 21528 itself that is 43992, so 21528 is abundant (43992 is more than 21528). Euler's totient φ(21528) = 6336 numbers up to 21528 share no factor with it.
- 4
The digits of 21528 add up to 18, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 118 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21528 = 2^{3} \times 3^{2} \times 13 \times 23 \]21528 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 48 |
| Sum of divisors | 65520 |
| Euler totient φ(n) | 6336 |
| Square | 463454784 |
| Cube | 9977254589952 |
| Square root | 146.724231 (= 6√598) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 118 |
| Scientific notation | 2.1528 × |
21528 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand five hundred and twenty-eight |
| Binary (base 2) | 101010000011000 |
| Octal (base 8) | 52030 |
| Hexadecimal (base 16) | 5418 |
| Base 3 | 1002112100 |
| As time | 21528 seconds = 5 h 58 min 48 s |
Is 21528 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21528 ÷ 2 = 10764) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21528 ÷ 3 = 7176) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (21528 ÷ 4 = 5382) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 3) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | Yes (21528 ÷ 6 = 3588) | 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 (21528 ÷ 8 = 2691) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (21528 ÷ 9 = 2392) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 8) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 1) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | Yes (21528 ÷ 12 = 1794) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21528 a prime number?
No. 21528 = × × 13 × 23, so it is divisible by 2.
What are the factors of 21528?
1, 2, 3, 4, 6, 8, 9, 12, 13, 18, 23, 24, 26, 36, 39, 46, 52, 69, 72, 78, 92, 104, 117, 138, 156, 184, 207, 234, 276, 299, 312, 414, 468, 552, 598, 828, 897, 936, 1196, 1656, 1794, 2392, 2691, 3588, 5382, 7176, 10764, 21528.
What is 21528 in binary?
101010000011000 (hexadecimal 5418, octal 52030).
What is the square root of 21528?
About 146.7242, exactly 6√598.
Is 21528 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 21528?
21528 is a triangular number: 1 + 2 + … + 207 = 21528; a Harshad number: divisible by its digit sum 18.