The number 21357
21357 is a composite number with 16 divisors. Its prime factorisation is × 7 × 113. Divisors (16): 1, 3, 7, 9, 21, 27, 63, 113, 189, 339, 791, 1017, 2373, 3051, 7119, 21357.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21357 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21357 is composite. Its prime factorisation is
- 3
The divisors add up to 36480; without 21357 itself that is 15123, so 21357 is deficient (15123 is less than 21357). Euler's totient φ(21357) = 12096 numbers up to 21357 share no factor with it.
- 4
The digits of 21357 add up to 18, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 48 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21357 = 3^{3} \times 7 \times 113 \]21357 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 36480 |
| Euler totient φ(n) | 12096 |
| Square | 456121449 |
| Cube | 9741385786293 |
| Square root | 146.140344 (= 3√2373) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 48 |
| Scientific notation | 2.1357 × |
21357 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand three hundred and fifty-seven |
| Binary (base 2) | 101001101101101 |
| Octal (base 8) | 51555 |
| Hexadecimal (base 16) | 536D |
| Base 3 | 1002022000 |
| As time | 21357 seconds = 5 h 55 min 57 s |
Is 21357 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 (21357 ÷ 3 = 7119) | 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 | No (remainder 2) | 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 | Yes (21357 ÷ 7 = 3051) | 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 | Yes (21357 ÷ 9 = 2373) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 7) | 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 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21357 a prime number?
No. 21357 = × 7 × 113, so it is divisible by 3.
What are the factors of 21357?
1, 3, 7, 9, 21, 27, 63, 113, 189, 339, 791, 1017, 2373, 3051, 7119, 21357.
What is 21357 in binary?
101001101101101 (hexadecimal 536D, octal 51555).
What is the square root of 21357?
About 146.1403, exactly 3√2373.
Is 21357 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 21357?
It is a composite number with 16 divisors.