The number 21967
21967 is a composite number with 4 divisors. Its prime factorisation is 11 × 1997. Divisors (4): 1, 11, 1997, 21967.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21967: a semiprime: 11 × 1997, the product of two primes.
- 2
21967 is composite. Its prime factorisation is
- 3
The divisors add up to 23976; without 21967 itself that is 2009, so 21967 is deficient (2009 is less than 21967). Euler's totient φ(21967) = 19960 numbers up to 21967 share no factor with it.
- 4
The digits of 21967 add up to 25, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 100 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21967 = 11 \times 1997 \]
21967 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 23976 |
| Euler totient φ(n) | 19960 |
| Square | 482549089 |
| Cube | 10600155838063 |
| Square root | 148.212685 |
| Digit sum / digital root | 25 / 7 |
| Collatz steps to 1 | 100 |
| Scientific notation | 2.1967 × |
21967 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand nine hundred and sixty-seven |
| Binary (base 2) | 101010111001111 |
| Octal (base 8) | 52717 |
| Hexadecimal (base 16) | 55CF |
| Base 3 | 1010010121 |
| As time | 21967 seconds = 6 h 6 min 7 s |
Is 21967 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 | No (remainder 2) | 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 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 7) | 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 7) | A number is divisible by 10 if the last digit is 0. |
| 11 | Yes (21967 ÷ 11 = 1997) | 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 21967 a prime number?
No. 21967 = 11 × 1997, so it is divisible by 11.
What are the factors of 21967?
1, 11, 1997, 21967.
What is 21967 in binary?
101010111001111 (hexadecimal 55CF, octal 52717).
What is the square root of 21967?
About 148.2127.
Is 21967 divisible by 3?
No. Its digits add up to 25, which is not a multiple of 3.
What is special about the number 21967?
21967 is a semiprime: 11 × 1997, the product of two primes.