The number 21556
21556 is a composite number with 12 divisors. Its prime factorisation is × 17 × 317. Divisors (12): 1, 2, 4, 17, 34, 68, 317, 634, 1268, 5389, 10778, 21556.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21556: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
21556 is composite. Its prime factorisation is
- 3
The divisors add up to 40068; without 21556 itself that is 18512, so 21556 is deficient (18512 is less than 21556). Euler's totient φ(21556) = 10112 numbers up to 21556 share no factor with it.
- 4
The digits of 21556 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 69 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21556 = 2^{2} \times 17 \times 317 \]21556 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 40068 |
| Euler totient φ(n) | 10112 |
| Square | 464661136 |
| Cube | 10016235447616 |
| Square root | 146.819617 (= 2√5389) |
| Digit sum / digital root | 19 / 1 |
| Collatz steps to 1 | 69 |
| Scientific notation | 2.1556 × |
21556 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand five hundred and fifty-six |
| Binary (base 2) | 101010000110100 |
| Octal (base 8) | 52064 |
| Hexadecimal (base 16) | 5434 |
| Base 3 | 1002120101 |
| As time | 21556 seconds = 5 h 59 min 16 s |
Is 21556 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21556 ÷ 2 = 10778) | 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 | Yes (21556 ÷ 4 = 5389) | 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 | No (remainder 3) | 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 4) | 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 6) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 7) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 4) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21556 a prime number?
No. 21556 = × 17 × 317, so it is divisible by 2.
What are the factors of 21556?
1, 2, 4, 17, 34, 68, 317, 634, 1268, 5389, 10778, 21556.
What is 21556 in binary?
101010000110100 (hexadecimal 5434, octal 52064).
What is the square root of 21556?
About 146.8196, exactly 2√5389.
Is 21556 divisible by 3?
No. Its digits add up to 19, which is not a multiple of 3.
What is special about the number 21556?
21556 is a happy number: repeatedly adding the squares of its digits reaches 1.