The number 21389
21389 is a composite number with 4 divisors. Its prime factorisation is 73 × 293. Divisors (4): 1, 73, 293, 21389.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21389: a semiprime: 73 × 293, the product of two primes.
- 2
21389 is composite. Its prime factorisation is
- 3
The divisors add up to 21756; without 21389 itself that is 367, so 21389 is deficient (367 is less than 21389). Euler's totient φ(21389) = 21024 numbers up to 21389 share no factor with it.
- 4
The digits of 21389 add up to 23, and repeating that until one digit is left gives the digital root 5. The Collatz sequence (halve if even, else 3n+1) takes 118 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21389 = 73 \times 293 \]
21389 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 21756 |
| Euler totient φ(n) | 21024 |
| Square | 457489321 |
| Cube | 9785239086869 |
| Square root | 146.249786 |
| Digit sum / digital root | 23 / 5 |
| Collatz steps to 1 | 118 |
| Scientific notation | 2.1389 × |
21389 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand three hundred and eighty-nine |
| Binary (base 2) | 101001110001101 |
| Octal (base 8) | 51615 |
| Hexadecimal (base 16) | 538D |
| Base 3 | 1002100012 |
| As time | 21389 seconds = 5 h 56 min 29 s |
Is 21389 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 2) | 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 5) | 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 5) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 5) | 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 5) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 5) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21389 a prime number?
No. 21389 = 73 × 293, so it is divisible by 73.
What are the factors of 21389?
1, 73, 293, 21389.
What is 21389 in binary?
101001110001101 (hexadecimal 538D, octal 51615).
What is the square root of 21389?
About 146.2498.
Is 21389 divisible by 3?
No. Its digits add up to 23, which is not a multiple of 3.
What is special about the number 21389?
21389 is a semiprime: 73 × 293, the product of two primes.