The number 55821
55821 is a composite number with 8 divisors. Its prime factorisation is 3 × 23 × 809. Divisors (8): 1, 3, 23, 69, 809, 2427, 18607, 55821.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
55821 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
55821 is composite. Its prime factorisation is
- 3
The divisors add up to 77760; without 55821 itself that is 21939, so 55821 is deficient (21939 is less than 55821). Euler's totient φ(55821) = 35552 numbers up to 55821 share no factor with it.
- 4
The digits of 55821 add up to 21, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 34 steps to reach 1.
LaTeX source of the formulas on this page
\[ 55821 = 3 \times 23 \times 809 \]
55821 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 77760 |
| Euler totient φ(n) | 35552 |
| Square | 3115984041 |
| Cube | 173937345152661 |
| Square root | 236.264682 |
| Digit sum / digital root | 21 / 3 |
| Collatz steps to 1 | 34 |
| Scientific notation | 5.5821 × |
55821 in other forms
| Form | Value |
|---|---|
| In words | fifty-five thousand eight hundred and twenty-one |
| Binary (base 2) | 1101101000001101 |
| Octal (base 8) | 155015 |
| Hexadecimal (base 16) | DA0D |
| Base 3 | 2211120110 |
| As time | 55821 seconds = 15 h 30 min 21 s |
Is 55821 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 | Yes (55821 ÷ 3 = 18607) | 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 1) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 3) | 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 5) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 3) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 1) | 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 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 55821 a prime number?
No. 55821 = 3 × 23 × 809, so it is divisible by 3.
What are the factors of 55821?
1, 3, 23, 69, 809, 2427, 18607, 55821.
What is 55821 in binary?
1101101000001101 (hexadecimal DA0D, octal 155015).
What is the square root of 55821?
About 236.2647.
Is 55821 divisible by 3?
Yes. Its digits add up to 21, a multiple of 3.
What is special about the number 55821?
It is a composite number with 8 divisors.