The number 21361
21361 is a composite number with 4 divisors. Its prime factorisation is 41 × 521. Divisors (4): 1, 41, 521, 21361.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21361: a semiprime: 41 × 521, the product of two primes.
- 2
21361 is composite. Its prime factorisation is
- 3
The divisors add up to 21924; without 21361 itself that is 563, so 21361 is deficient (563 is less than 21361). Euler's totient φ(21361) = 20800 numbers up to 21361 share no factor with it.
- 4
The digits of 21361 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 149 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21361 = 41 \times 521 \]
21361 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 21924 |
| Euler totient φ(n) | 20800 |
| Square | 456292321 |
| Cube | 9746860268881 |
| Square root | 146.154028 |
| Digit sum / digital root | 13 / 4 |
| Collatz steps to 1 | 149 |
| Scientific notation | 2.1361 × |
21361 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand three hundred and sixty-one |
| Binary (base 2) | 101001101110001 |
| Octal (base 8) | 51561 |
| Hexadecimal (base 16) | 5371 |
| Base 3 | 1002022011 |
| As time | 21361 seconds = 5 h 56 min 1 s |
Is 21361 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 4) | 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 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 | No (remainder 10) | 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 21361 a prime number?
No. 21361 = 41 × 521, so it is divisible by 41.
What are the factors of 21361?
1, 41, 521, 21361.
What is 21361 in binary?
101001101110001 (hexadecimal 5371, octal 51561).
What is the square root of 21361?
About 146.1540.
Is 21361 divisible by 3?
No. Its digits add up to 13, which is not a multiple of 3.
What is special about the number 21361?
21361 is a semiprime: 41 × 521, the product of two primes.