The number 21995
21995 is a composite number with 8 divisors. Its prime factorisation is 5 × 53 × 83. Divisors (8): 1, 5, 53, 83, 265, 415, 4399, 21995.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21995: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
21995 is composite. Its prime factorisation is
- 3
The divisors add up to 27216; without 21995 itself that is 5221, so 21995 is deficient (5221 is less than 21995). Euler's totient φ(21995) = 17056 numbers up to 21995 share no factor with it.
- 4
The digits of 21995 add up to 26, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 149 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21995 = 5 \times 53 \times 83 \]
21995 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 27216 |
| Euler totient φ(n) | 17056 |
| Square | 483780025 |
| Cube | 10640741649875 |
| Square root | 148.307114 |
| Digit sum / digital root | 26 / 8 |
| Collatz steps to 1 | 149 |
| Scientific notation | 2.1995 × |
21995 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand nine hundred and ninety-five |
| Binary (base 2) | 101010111101011 |
| Octal (base 8) | 52753 |
| Hexadecimal (base 16) | 55EB |
| Base 3 | 1010011122 |
| As time | 21995 seconds = 6 h 6 min 35 s |
Is 21995 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 2) | 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 (21995 ÷ 5 = 4399) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 5) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 1) | 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 8) | 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 | No (remainder 6) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 11) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21995 a prime number?
No. 21995 = 5 × 53 × 83, so it is divisible by 5.
What are the factors of 21995?
1, 5, 53, 83, 265, 415, 4399, 21995.
What is 21995 in binary?
101010111101011 (hexadecimal 55EB, octal 52753).
What is the square root of 21995?
About 148.3071.
Is 21995 divisible by 3?
No. Its digits add up to 26, which is not a multiple of 3.
What is special about the number 21995?
21995 is a happy number: repeatedly adding the squares of its digits reaches 1.