The number 21351
21351 is a composite number with 8 divisors. Its prime factorisation is 3 × 11 × 647. Divisors (8): 1, 3, 11, 33, 647, 1941, 7117, 21351.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21351 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21351 is composite. Its prime factorisation is
- 3
The divisors add up to 31104; without 21351 itself that is 9753, so 21351 is deficient (9753 is less than 21351). Euler's totient φ(21351) = 12920 numbers up to 21351 share no factor with it.
- 4
The digits of 21351 add up to 12, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 255 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21351 = 3 \times 11 \times 647 \]
21351 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 31104 |
| Euler totient φ(n) | 12920 |
| Square | 455865201 |
| Cube | 9733177906551 |
| Square root | 146.119814 |
| Digit sum / digital root | 12 / 3 |
| Collatz steps to 1 | 255 |
| Scientific notation | 2.1351 × |
21351 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand three hundred and fifty-one |
| Binary (base 2) | 101001101100111 |
| Octal (base 8) | 51547 |
| Hexadecimal (base 16) | 5367 |
| Base 3 | 1002021210 |
| As time | 21351 seconds = 5 h 55 min 51 s |
Is 21351 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 (21351 ÷ 3 = 7117) | 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 | No (remainder 1) | 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 1) | 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 3) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 1) | A number is divisible by 10 if the last digit is 0. |
| 11 | Yes (21351 ÷ 11 = 1941) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21351 a prime number?
No. 21351 = 3 × 11 × 647, so it is divisible by 3.
What are the factors of 21351?
1, 3, 11, 33, 647, 1941, 7117, 21351.
What is 21351 in binary?
101001101100111 (hexadecimal 5367, octal 51547).
What is the square root of 21351?
About 146.1198.
Is 21351 divisible by 3?
Yes. Its digits add up to 12, a multiple of 3.
What is special about the number 21351?
It is a composite number with 8 divisors.