The number 21901
21901 is a composite number with 6 divisors. Its prime factorisation is Ć 181. Divisors (6): 1, 11, 121, 181, 1991, 21901.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21901 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21901 is composite. Its prime factorisation is
- 3
The divisors add up to 24206; without 21901 itself that is 2305, so 21901 is deficient (2305 is less than 21901). Euler's totient Ļ(21901) = 19800 numbers up to 21901 share no factor with it.
- 4
The digits of 21901 add up to 13, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 43 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21901 = 11^{2} \times 181 \]21901 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 6 |
| Sum of divisors | 24206 |
| Euler totient Ļ(n) | 19800 |
| Square | 479653801 |
| Cube | 10504897895701 |
| Square root | 147.989865 (= 11ā181) |
| Digit sum / digital root | 13 / 4 |
| Collatz steps to 1 | 43 |
| Scientific notation | 2.1901 Ć |
21901 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand nine hundred and one |
| Binary (base 2) | 101010110001101 |
| Octal (base 8) | 52615 |
| Hexadecimal (base 16) | 558D |
| Base 3 | 1010001011 |
| As time | 21901 seconds = 6 h 5 min 1 s |
Is 21901 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 1) | 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 1) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 1) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 5) | 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 4) | 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 (21901 Ć· 11 = 1991) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 1) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21901 a prime number?
No. 21901 = Ć 181, so it is divisible by 11.
What are the factors of 21901?
1, 11, 121, 181, 1991, 21901.
What is 21901 in binary?
101010110001101 (hexadecimal 558D, octal 52615).
What is the square root of 21901?
About 147.9899, exactly 11ā181.
Is 21901 divisible by 3?
No. Its digits add up to 13, which is not a multiple of 3.
What is special about the number 21901?
It is a composite number with 6 divisors.