The number 21775
21775 is a composite number with 12 divisors. Its prime factorisation is × 13 × 67. Divisors (12): 1, 5, 13, 25, 65, 67, 325, 335, 871, 1675, 4355, 21775.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21775 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21775 is composite. Its prime factorisation is
- 3
The divisors add up to 29512; without 21775 itself that is 7737, so 21775 is deficient (7737 is less than 21775). Euler's totient φ(21775) = 15840 numbers up to 21775 share no factor with it.
- 4
The digits of 21775 add up to 22, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 118 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21775 = 5^{2} \times 13 \times 67 \]21775 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 29512 |
| Euler totient φ(n) | 15840 |
| Square | 474150625 |
| Cube | 10324629859375 |
| Square root | 147.563546 (= 5√871) |
| Digit sum / digital root | 22 / 4 |
| Collatz steps to 1 | 118 |
| Scientific notation | 2.1775 × |
21775 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand seven hundred and seventy-five |
| Binary (base 2) | 101010100001111 |
| Octal (base 8) | 52417 |
| Hexadecimal (base 16) | 550F |
| Base 3 | 1002212111 |
| As time | 21775 seconds = 6 h 2 min 55 s |
Is 21775 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 (21775 ÷ 5 = 4355) | 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 5) | 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 4) | 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 7) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21775 a prime number?
No. 21775 = × 13 × 67, so it is divisible by 5.
What are the factors of 21775?
1, 5, 13, 25, 65, 67, 325, 335, 871, 1675, 4355, 21775.
What is 21775 in binary?
101010100001111 (hexadecimal 550F, octal 52417).
What is the square root of 21775?
About 147.5635, exactly 5√871.
Is 21775 divisible by 3?
No. Its digits add up to 22, which is not a multiple of 3.
What is special about the number 21775?
It is a composite number with 12 divisors.