The number 21835
21835 is a composite number with 8 divisors. Its prime factorisation is 5 × 11 × 397. Divisors (8): 1, 5, 11, 55, 397, 1985, 4367, 21835.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21835: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
21835 is composite. Its prime factorisation is
- 3
The divisors add up to 28656; without 21835 itself that is 6821, so 21835 is deficient (6821 is less than 21835). Euler's totient φ(21835) = 15840 numbers up to 21835 share no factor with it.
- 4
The digits of 21835 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
\[ 21835 = 5 \times 11 \times 397 \]
21835 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 28656 |
| Euler totient φ(n) | 15840 |
| Square | 476767225 |
| Cube | 10410212357875 |
| Square root | 147.766708 |
| Digit sum / digital root | 19 / 1 |
| Collatz steps to 1 | 69 |
| Scientific notation | 2.1835 × |
21835 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand eight hundred and thirty-five |
| Binary (base 2) | 101010101001011 |
| Octal (base 8) | 52513 |
| Hexadecimal (base 16) | 554B |
| Base 3 | 1002221201 |
| As time | 21835 seconds = 6 h 3 min 55 s |
Is 21835 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 3) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (21835 ÷ 5 = 4367) | 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 | No (remainder 2) | 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 3) | 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 5) | A number is divisible by 10 if the last digit is 0. |
| 11 | Yes (21835 ÷ 11 = 1985) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 7) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21835 a prime number?
No. 21835 = 5 × 11 × 397, so it is divisible by 5.
What are the factors of 21835?
1, 5, 11, 55, 397, 1985, 4367, 21835.
What is 21835 in binary?
101010101001011 (hexadecimal 554B, octal 52513).
What is the square root of 21835?
About 147.7667.
Is 21835 divisible by 3?
No. Its digits add up to 19, which is not a multiple of 3.
What is special about the number 21835?
21835 is a happy number: repeatedly adding the squares of its digits reaches 1.