The number 21398
21398 is a composite number with 8 divisors. Its prime factorisation is 2 × 13 × 823. Divisors (8): 1, 2, 13, 26, 823, 1646, 10699, 21398.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21398 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21398 is composite. Its prime factorisation is
- 3
The divisors add up to 34608; without 21398 itself that is 13210, so 21398 is deficient (13210 is less than 21398). Euler's totient φ(21398) = 9864 numbers up to 21398 share no factor with it.
- 4
The digits of 21398 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 48 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21398 = 2 \times 13 \times 823 \]
21398 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 34608 |
| Euler totient φ(n) | 9864 |
| Square | 457874404 |
| Cube | 9797596496792 |
| Square root | 146.280552 |
| Digit sum / digital root | 23 / 5 |
| Collatz steps to 1 | 48 |
| Scientific notation | 2.1398 × |
21398 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand three hundred and ninety-eight |
| Binary (base 2) | 101001110010110 |
| Octal (base 8) | 51626 |
| Hexadecimal (base 16) | 5396 |
| Base 3 | 1002100112 |
| As time | 21398 seconds = 5 h 56 min 38 s |
Is 21398 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21398 ÷ 2 = 10699) | 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 2) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 3) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 2) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 6) | 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 6) | 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 8) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 3) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 2) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21398 a prime number?
No. 21398 = 2 × 13 × 823, so it is divisible by 2.
What are the factors of 21398?
1, 2, 13, 26, 823, 1646, 10699, 21398.
What is 21398 in binary?
101001110010110 (hexadecimal 5396, octal 51626).
What is the square root of 21398?
About 146.2806.
Is 21398 divisible by 3?
No. Its digits add up to 23, which is not a multiple of 3.
What is special about the number 21398?
It is a composite number with 8 divisors.