The number 23821
23821 is a composite number with 8 divisors. Its prime factorisation is 7 × 41 × 83. Divisors (8): 1, 7, 41, 83, 287, 581, 3403, 23821.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 23821: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
23821 is composite. Its prime factorisation is
- 3
The divisors add up to 28224; without 23821 itself that is 4403, so 23821 is deficient (4403 is less than 23821). Euler's totient φ(23821) = 19680 numbers up to 23821 share no factor with it.
- 4
The digits of 23821 add up to 16, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 144 steps to reach 1.
LaTeX source of the formulas on this page
\[ 23821 = 7 \times 41 \times 83 \]
23821 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 28224 |
| Euler totient φ(n) | 19680 |
| Square | 567440041 |
| Cube | 13516989216661 |
| Square root | 154.340533 |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 144 |
| Scientific notation | 2.3821 × |
23821 in other forms
| Form | Value |
|---|---|
| In words | twenty-three thousand eight hundred and twenty-one |
| Binary (base 2) | 101110100001101 |
| Octal (base 8) | 56415 |
| Hexadecimal (base 16) | 5D0D |
| Base 3 | 1012200021 |
| As time | 23821 seconds = 6 h 37 min 1 s |
Is 23821 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 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 1) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | Yes (23821 ÷ 7 = 3403) | 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 7) | 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 6) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 1) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 23821 a prime number?
No. 23821 = 7 × 41 × 83, so it is divisible by 7.
What are the factors of 23821?
1, 7, 41, 83, 287, 581, 3403, 23821.
What is 23821 in binary?
101110100001101 (hexadecimal 5D0D, octal 56415).
What is the square root of 23821?
About 154.3405.
Is 23821 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 23821?
23821 is a happy number: repeatedly adding the squares of its digits reaches 1.