The number 21439
21439 is a composite number with 4 divisors. Its prime factorisation is 11 × 1949. Divisors (4): 1, 11, 1949, 21439.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21439: a semiprime: 11 × 1949, the product of two primes.
- 2
21439 is composite. Its prime factorisation is
- 3
The divisors add up to 23400; without 21439 itself that is 1961, so 21439 is deficient (1961 is less than 21439). Euler's totient φ(21439) = 19480 numbers up to 21439 share no factor with it.
- 4
The digits of 21439 add up to 19, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 74 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21439 = 11 \times 1949 \]
21439 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 23400 |
| Euler totient φ(n) | 19480 |
| Square | 459630721 |
| Cube | 9854023027519 |
| Square root | 146.420627 |
| Digit sum / digital root | 19 / 1 |
| Collatz steps to 1 | 74 |
| Scientific notation | 2.1439 × |
21439 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand four hundred and thirty-nine |
| Binary (base 2) | 101001110111111 |
| Octal (base 8) | 51677 |
| Hexadecimal (base 16) | 53BF |
| Base 3 | 1002102001 |
| As time | 21439 seconds = 5 h 57 min 19 s |
Is 21439 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 3) | 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 5) | 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 1) | 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 | Yes (21439 ÷ 11 = 1949) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 7) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21439 a prime number?
No. 21439 = 11 × 1949, so it is divisible by 11.
What are the factors of 21439?
1, 11, 1949, 21439.
What is 21439 in binary?
101001110111111 (hexadecimal 53BF, octal 51677).
What is the square root of 21439?
About 146.4206.
Is 21439 divisible by 3?
No. Its digits add up to 19, which is not a multiple of 3.
What is special about the number 21439?
21439 is a semiprime: 11 × 1949, the product of two primes.