The number 21485
21485 is a composite number with 4 divisors. Its prime factorisation is 5 × 4297. Divisors (4): 1, 5, 4297, 21485.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21485: a semiprime: 5 × 4297, the product of two primes.
- 2
21485 is composite. Its prime factorisation is
- 3
The divisors add up to 25788; without 21485 itself that is 4303, so 21485 is deficient (4303 is less than 21485). Euler's totient φ(21485) = 17184 numbers up to 21485 share no factor with it.
- 4
The digits of 21485 add up to 20, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 131 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21485 = 5 \times 4297 \]
21485 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 25788 |
| Euler totient φ(n) | 17184 |
| Square | 461605225 |
| Cube | 9917588259125 |
| Square root | 146.577624 |
| Digit sum / digital root | 20 / 2 |
| Collatz steps to 1 | 131 |
| Scientific notation | 2.1485 × |
21485 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand four hundred and eighty-five |
| Binary (base 2) | 101001111101101 |
| Octal (base 8) | 51755 |
| Hexadecimal (base 16) | 53ED |
| Base 3 | 1002110202 |
| As time | 21485 seconds = 5 h 58 min 5 s |
Is 21485 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 (21485 ÷ 5 = 4297) | 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 2) | 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 2) | 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 2) | 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 21485 a prime number?
No. 21485 = 5 × 4297, so it is divisible by 5.
What are the factors of 21485?
1, 5, 4297, 21485.
What is 21485 in binary?
101001111101101 (hexadecimal 53ED, octal 51755).
What is the square root of 21485?
About 146.5776.
Is 21485 divisible by 3?
No. Its digits add up to 20, which is not a multiple of 3.
What is special about the number 21485?
21485 is a semiprime: 5 × 4297, the product of two primes.