The number 21375
21375 is a composite number with 24 divisors. Its prime factorisation is × × 19. Divisors (24): 1, 3, 5, 9, 15, 19, 25, 45, 57, 75, 95, 125, 171, 225, 285, 375 … 21375.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21375 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21375 is composite. Its prime factorisation is
- 3
The divisors add up to 40560; without 21375 itself that is 19185, so 21375 is deficient (19185 is less than 21375). Euler's totient φ(21375) = 10800 numbers up to 21375 share no factor with it.
- 4
The digits of 21375 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 100 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21375 = 3^{2} \times 5^{3} \times 19 \]21375 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 40560 |
| Euler totient φ(n) | 10800 |
| Square | 456890625 |
| Cube | 9766037109375 |
| Square root | 146.201915 (= 15√95) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 100 |
| Scientific notation | 2.1375 × |
21375 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand three hundred and seventy-five |
| Binary (base 2) | 101001101111111 |
| Octal (base 8) | 51577 |
| Hexadecimal (base 16) | 537F |
| Base 3 | 1002022200 |
| As time | 21375 seconds = 5 h 56 min 15 s |
Is 21375 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | No (remainder 1) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21375 ÷ 3 = 7125) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 3) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (21375 ÷ 5 = 4275) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 3) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 4) | 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 7) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (21375 ÷ 9 = 2375) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 5) | 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 | No (remainder 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21375 a prime number?
No. 21375 = × × 19, so it is divisible by 3.
What are the factors of 21375?
1, 3, 5, 9, 15, 19, 25, 45, 57, 75, 95, 125, 171, 225, 285, 375, 475, 855, 1125, 1425, 2375, 4275, 7125, 21375.
What is 21375 in binary?
101001101111111 (hexadecimal 537F, octal 51577).
What is the square root of 21375?
About 146.2019, exactly 15√95.
Is 21375 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 21375?
It is a composite number with 24 divisors.