The number 21395
21395 is a composite number with 8 divisors. Its prime factorisation is 5 × 11 × 389. Divisors (8): 1, 5, 11, 55, 389, 1945, 4279, 21395.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21395 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21395 is composite. Its prime factorisation is
- 3
The divisors add up to 28080; without 21395 itself that is 6685, so 21395 is deficient (6685 is less than 21395). Euler's totient φ(21395) = 15520 numbers up to 21395 share no factor with it.
- 4
The digits of 21395 add up to 20, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 193 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21395 = 5 \times 11 \times 389 \]
21395 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 28080 |
| Euler totient φ(n) | 15520 |
| Square | 457746025 |
| Cube | 9793476204875 |
| Square root | 146.270298 |
| Digit sum / digital root | 20 / 2 |
| Collatz steps to 1 | 193 |
| Scientific notation | 2.1395 × |
21395 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand three hundred and ninety-five |
| Binary (base 2) | 101001110010011 |
| Octal (base 8) | 51623 |
| Hexadecimal (base 16) | 5393 |
| Base 3 | 1002100102 |
| As time | 21395 seconds = 5 h 56 min 35 s |
Is 21395 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 (21395 ÷ 5 = 4279) | 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 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 3) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 2) | 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 (21395 ÷ 11 = 1945) | 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 21395 a prime number?
No. 21395 = 5 × 11 × 389, so it is divisible by 5.
What are the factors of 21395?
1, 5, 11, 55, 389, 1945, 4279, 21395.
What is 21395 in binary?
101001110010011 (hexadecimal 5393, octal 51623).
What is the square root of 21395?
About 146.2703.
Is 21395 divisible by 3?
No. Its digits add up to 20, which is not a multiple of 3.
What is special about the number 21395?
It is a composite number with 8 divisors.