The number 13921
13921 is the 1646th prime number. Its only divisors are 1 and 13921.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 13921: the 1646th prime number.
- 2
13921 is prime, so its only factors are 1 and 13921. It is the 1646th prime; the next prime is 13931 and the one before is 13913.
- 3
The divisors add up to 13922; without 13921 itself that is 1, so 13921 is deficient (1 is less than 13921). Euler's totient φ(13921) = 13920 numbers up to 13921 share no factor with it.
- 4
The digits of 13921 add up to 16, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 107 steps to reach 1.
13921 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 13922 |
| Euler totient φ(n) | 13920 |
| Square | 193794241 |
| Cube | 2697809628961 |
| Square root | 117.987287 |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 107 |
| Scientific notation | 1.3921 × |
13921 in other forms
| Form | Value |
|---|---|
| In words | thirteen thousand nine hundred and twenty-one |
| Binary (base 2) | 11011001100001 |
| Octal (base 8) | 33141 |
| Hexadecimal (base 16) | 3661 |
| Base 3 | 201002121 |
| As time | 13921 seconds = 3 h 52 min 1 s |
Is 13921 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 7) | 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 6) | 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 13921 a prime number?
Yes. 13921 is divisible only by 1 and itself.
What are the factors of 13921?
1, 13921.
What is 13921 in binary?
11011001100001 (hexadecimal 3661, octal 33141).
What is the square root of 13921?
About 117.9873.
Is 13921 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 13921?
13921 is the 1646th prime number.