The number 21289
21289 is a composite number with 4 divisors. Its prime factorisation is 61 × 349. Divisors (4): 1, 61, 349, 21289.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21289: a semiprime: 61 × 349, the product of two primes.
- 2
21289 is composite. Its prime factorisation is
- 3
The divisors add up to 21700; without 21289 itself that is 411, so 21289 is deficient (411 is less than 21289). Euler's totient φ(21289) = 20880 numbers up to 21289 share no factor with it.
- 4
The digits of 21289 add up to 22, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 56 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21289 = 61 \times 349 \]
21289 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 21700 |
| Euler totient φ(n) | 20880 |
| Square | 453221521 |
| Cube | 9648632960569 |
| Square root | 145.907505 |
| Digit sum / digital root | 22 / 4 |
| Collatz steps to 1 | 56 |
| Scientific notation | 2.1289 × |
21289 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand two hundred and eighty-nine |
| Binary (base 2) | 101001100101001 |
| Octal (base 8) | 51451 |
| Hexadecimal (base 16) | 5329 |
| Base 3 | 1002012111 |
| As time | 21289 seconds = 5 h 54 min 49 s |
Is 21289 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 | No (remainder 1) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 1) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 4) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 1) | 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 4) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 9) | 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 1) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21289 a prime number?
No. 21289 = 61 × 349, so it is divisible by 61.
What are the factors of 21289?
1, 61, 349, 21289.
What is 21289 in binary?
101001100101001 (hexadecimal 5329, octal 51451).
What is the square root of 21289?
About 145.9075.
Is 21289 divisible by 3?
No. Its digits add up to 22, which is not a multiple of 3.
What is special about the number 21289?
21289 is a semiprime: 61 × 349, the product of two primes.