The number 21135
21135 is a composite number with 8 divisors. Its prime factorisation is 3 × 5 × 1409. Divisors (8): 1, 3, 5, 15, 1409, 4227, 7045, 21135.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21135 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21135 is composite. Its prime factorisation is
- 3
The divisors add up to 33840; without 21135 itself that is 12705, so 21135 is deficient (12705 is less than 21135). Euler's totient φ(21135) = 11264 numbers up to 21135 share no factor with it.
- 4
The digits of 21135 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 61 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21135 = 3 \times 5 \times 1409 \]
21135 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 33840 |
| Euler totient φ(n) | 11264 |
| Square | 446688225 |
| Cube | 9440755635375 |
| Square root | 145.378816 |
| Digit sum / digital root | 12 / 3 |
| Collatz steps to 1 | 61 |
| Scientific notation | 2.1135 × |
21135 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand one hundred and thirty-five |
| Binary (base 2) | 101001010001111 |
| Octal (base 8) | 51217 |
| Hexadecimal (base 16) | 528F |
| Base 3 | 1001222210 |
| As time | 21135 seconds = 5 h 52 min 15 s |
Is 21135 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 (21135 ÷ 3 = 7045) | 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 (21135 ÷ 5 = 4227) | 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 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 | No (remainder 7) | 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 | No (remainder 5) | 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 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21135 a prime number?
No. 21135 = 3 × 5 × 1409, so it is divisible by 3.
What are the factors of 21135?
1, 3, 5, 15, 1409, 4227, 7045, 21135.
What is 21135 in binary?
101001010001111 (hexadecimal 528F, octal 51217).
What is the square root of 21135?
About 145.3788.
Is 21135 divisible by 3?
Yes. Its digits add up to 12, a multiple of 3.
What is special about the number 21135?
It is a composite number with 8 divisors.