The number 21725
21725 is a composite number with 12 divisors. Its prime factorisation is × 11 × 79. Divisors (12): 1, 5, 11, 25, 55, 79, 275, 395, 869, 1975, 4345, 21725.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21725 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21725 is composite. Its prime factorisation is
- 3
The divisors add up to 29760; without 21725 itself that is 8035, so 21725 is deficient (8035 is less than 21725). Euler's totient φ(21725) = 15600 numbers up to 21725 share no factor with it.
- 4
The digits of 21725 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 100 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21725 = 5^{2} \times 11 \times 79 \]21725 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 29760 |
| Euler totient φ(n) | 15600 |
| Square | 471975625 |
| Cube | 10253670453125 |
| Square root | 147.394030 (= 5√869) |
| Digit sum / digital root | 17 / 8 |
| Collatz steps to 1 | 100 |
| Scientific notation | 2.1725 × |
21725 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand seven hundred and twenty-five |
| Binary (base 2) | 101010011011101 |
| Octal (base 8) | 52335 |
| Hexadecimal (base 16) | 54DD |
| Base 3 | 1002210122 |
| As time | 21725 seconds = 6 h 2 min 5 s |
Is 21725 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 1) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (21725 ÷ 5 = 4345) | 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 4) | 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 5) | 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 5) | A number is divisible by 10 if the last digit is 0. |
| 11 | Yes (21725 ÷ 11 = 1975) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 5) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21725 a prime number?
No. 21725 = × 11 × 79, so it is divisible by 5.
What are the factors of 21725?
1, 5, 11, 25, 55, 79, 275, 395, 869, 1975, 4345, 21725.
What is 21725 in binary?
101010011011101 (hexadecimal 54DD, octal 52335).
What is the square root of 21725?
About 147.3940, exactly 5√869.
Is 21725 divisible by 3?
No. Its digits add up to 17, which is not a multiple of 3.
What is special about the number 21725?
It is a composite number with 12 divisors.