The number 21406
21406 is a composite number with 16 divisors. Its prime factorisation is 2 × 7 × 11 × 139. Divisors (16): 1, 2, 7, 11, 14, 22, 77, 139, 154, 278, 973, 1529, 1946, 3058, 10703, 21406.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21406 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21406 is composite. Its prime factorisation is
- 3
The divisors add up to 40320; without 21406 itself that is 18914, so 21406 is deficient (18914 is less than 21406). Euler's totient φ(21406) = 8280 numbers up to 21406 share no factor with it.
- 4
The digits of 21406 add up to 13, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 193 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21406 = 2 \times 7 \times 11 \times 139 \]
21406 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 40320 |
| Euler totient φ(n) | 8280 |
| Square | 458216836 |
| Cube | 9808589591416 |
| Square root | 146.307895 |
| Digit sum / digital root | 13 / 4 |
| Collatz steps to 1 | 193 |
| Scientific notation | 2.1406 × |
21406 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand four hundred and six |
| Binary (base 2) | 101001110011110 |
| Octal (base 8) | 51636 |
| Hexadecimal (base 16) | 539E |
| Base 3 | 1002100211 |
| As time | 21406 seconds = 5 h 56 min 46 s |
Is 21406 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21406 ÷ 2 = 10703) | 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 2) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 1) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 4) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | Yes (21406 ÷ 7 = 3058) | 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 4) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 6) | A number is divisible by 10 if the last digit is 0. |
| 11 | Yes (21406 ÷ 11 = 1946) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 10) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21406 a prime number?
No. 21406 = 2 × 7 × 11 × 139, so it is divisible by 2.
What are the factors of 21406?
1, 2, 7, 11, 14, 22, 77, 139, 154, 278, 973, 1529, 1946, 3058, 10703, 21406.
What is 21406 in binary?
101001110011110 (hexadecimal 539E, octal 51636).
What is the square root of 21406?
About 146.3079.
Is 21406 divisible by 3?
No. Its digits add up to 13, which is not a multiple of 3.
What is special about the number 21406?
It is a composite number with 16 divisors.