The number 21175
21175 is a composite number with 18 divisors. Its prime factorisation is × 7 × . Divisors (18): 1, 5, 7, 11, 25, 35, 55, 77, 121, 175, 275, 385, 605, 847, 1925, 3025 … 21175.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21175 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21175 is composite. Its prime factorisation is
- 3
The divisors add up to 32984; without 21175 itself that is 11809, so 21175 is deficient (11809 is less than 21175). Euler's totient φ(21175) = 13200 numbers up to 21175 share no factor with it.
- 4
The digits of 21175 add up to 16, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 131 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21175 = 5^{2} \times 7 \times 11^{2} \]21175 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 18 |
| Sum of divisors | 32984 |
| Euler totient φ(n) | 13200 |
| Square | 448380625 |
| Cube | 9494459734375 |
| Square root | 145.516322 (= 55√7) |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 131 |
| Scientific notation | 2.1175 × |
21175 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand one hundred and seventy-five |
| Binary (base 2) | 101001010110111 |
| Octal (base 8) | 51267 |
| Hexadecimal (base 16) | 52B7 |
| Base 3 | 1002001021 |
| As time | 21175 seconds = 5 h 52 min 55 s |
Is 21175 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 (21175 ÷ 5 = 4235) | 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 | Yes (21175 ÷ 7 = 3025) | 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 5) | A number is divisible by 10 if the last digit is 0. |
| 11 | Yes (21175 ÷ 11 = 1925) | 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 21175 a prime number?
No. 21175 = × 7 × , so it is divisible by 5.
What are the factors of 21175?
1, 5, 7, 11, 25, 35, 55, 77, 121, 175, 275, 385, 605, 847, 1925, 3025, 4235, 21175.
What is 21175 in binary?
101001010110111 (hexadecimal 52B7, octal 51267).
What is the square root of 21175?
About 145.5163, exactly 55√7.
Is 21175 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 21175?
It is a composite number with 18 divisors.