The number 21131
21131 is a composite number with 8 divisors. Its prime factorisation is 11 × 17 × 113. Divisors (8): 1, 11, 17, 113, 187, 1243, 1921, 21131.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21131 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21131 is composite. Its prime factorisation is
- 3
The divisors add up to 24624; without 21131 itself that is 3493, so 21131 is deficient (3493 is less than 21131). Euler's totient φ(21131) = 17920 numbers up to 21131 share no factor with it.
- 4
The digits of 21131 add up to 8, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 56 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21131 = 11 \times 17 \times 113 \]
21131 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 24624 |
| Euler totient φ(n) | 17920 |
| Square | 446519161 |
| Cube | 9435396391091 |
| Square root | 145.365058 |
| Digit sum / digital root | 8 / 8 |
| Collatz steps to 1 | 56 |
| Scientific notation | 2.1131 × |
21131 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand one hundred and thirty-one |
| Binary (base 2) | 101001010001011 |
| Octal (base 8) | 51213 |
| Hexadecimal (base 16) | 528B |
| Base 3 | 1001222122 |
| As time | 21131 seconds = 5 h 52 min 11 s |
Is 21131 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 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 5) | 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 3) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 8) | 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 (21131 ÷ 11 = 1921) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 11) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21131 a prime number?
No. 21131 = 11 × 17 × 113, so it is divisible by 11.
What are the factors of 21131?
1, 11, 17, 113, 187, 1243, 1921, 21131.
What is 21131 in binary?
101001010001011 (hexadecimal 528B, octal 51213).
What is the square root of 21131?
About 145.3651.
Is 21131 divisible by 3?
No. Its digits add up to 8, which is not a multiple of 3.
What is special about the number 21131?
It is a composite number with 8 divisors.