The number 21671
21671 is a composite number with 4 divisors. Its prime factorisation is 13 × 1667. Divisors (4): 1, 13, 1667, 21671.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21671: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 13 × 1667, the product of two primes.
- 2
21671 is composite. Its prime factorisation is
- 3
The divisors add up to 23352; without 21671 itself that is 1681, so 21671 is deficient (1681 is less than 21671). Euler's totient φ(21671) = 19992 numbers up to 21671 share no factor with it.
- 4
The digits of 21671 add up to 17, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 154 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21671 = 13 \times 1667 \]
21671 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 23352 |
| Euler totient φ(n) | 19992 |
| Square | 469632241 |
| Cube | 10177400294711 |
| Square root | 147.210733 |
| Digit sum / digital root | 17 / 8 |
| Collatz steps to 1 | 154 |
| Scientific notation | 2.1671 × |
21671 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand six hundred and seventy-one |
| Binary (base 2) | 101010010100111 |
| Octal (base 8) | 52247 |
| Hexadecimal (base 16) | 54A7 |
| Base 3 | 1002201122 |
| As time | 21671 seconds = 6 h 1 min 11 s |
Is 21671 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 | No (remainder 1) | 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 6) | 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 8) | 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 1) | 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 21671 a prime number?
No. 21671 = 13 × 1667, so it is divisible by 13.
What are the factors of 21671?
1, 13, 1667, 21671.
What is 21671 in binary?
101010010100111 (hexadecimal 54A7, octal 52247).
What is the square root of 21671?
About 147.2107.
Is 21671 divisible by 3?
No. Its digits add up to 17, which is not a multiple of 3.
What is special about the number 21671?
21671 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 13 × 1667, the product of two primes.