The number 21345
21345 is a composite number with 8 divisors. Its prime factorisation is 3 × 5 × 1423. Divisors (8): 1, 3, 5, 15, 1423, 4269, 7115, 21345.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21345: a Harshad number: divisible by its digit sum 15.
- 2
21345 is composite. Its prime factorisation is
- 3
The divisors add up to 34176; without 21345 itself that is 12831, so 21345 is deficient (12831 is less than 21345). Euler's totient φ(21345) = 11376 numbers up to 21345 share no factor with it.
- 4
The digits of 21345 add up to 15, and repeating that until one digit is left gives the digital root 6. The Collatz sequence (halve if even, else 3n+1) takes 74 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21345 = 3 \times 5 \times 1423 \]
21345 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 34176 |
| Euler totient φ(n) | 11376 |
| Square | 455609025 |
| Cube | 9724974638625 |
| Square root | 146.099281 |
| Digit sum / digital root | 15 / 6 |
| Collatz steps to 1 | 74 |
| Scientific notation | 2.1345 × |
21345 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand three hundred and forty-five |
| Binary (base 2) | 101001101100001 |
| Octal (base 8) | 51541 |
| Hexadecimal (base 16) | 5361 |
| Base 3 | 1002021120 |
| As time | 21345 seconds = 5 h 55 min 45 s |
Is 21345 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 | Yes (21345 ÷ 3 = 7115) | 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 (21345 ÷ 5 = 4269) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 3) | 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 6) | 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 5) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21345 a prime number?
No. 21345 = 3 × 5 × 1423, so it is divisible by 3.
What are the factors of 21345?
1, 3, 5, 15, 1423, 4269, 7115, 21345.
What is 21345 in binary?
101001101100001 (hexadecimal 5361, octal 51541).
What is the square root of 21345?
About 146.0993.
Is 21345 divisible by 3?
Yes. Its digits add up to 15, a multiple of 3.
What is special about the number 21345?
21345 is a Harshad number: divisible by its digit sum 15.