The number 16381
16381 is the 1900th prime number. Its only divisors are 1 and 16381.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 16381: the 1900th prime number.
- 2
16381 is prime, so its only factors are 1 and 16381. It is the 1900th prime; the next prime is 16411 and the one before is 16369.
- 3
The divisors add up to 16382; without 16381 itself that is 1, so 16381 is deficient (1 is less than 16381). Euler's totient φ(16381) = 16380 numbers up to 16381 share no factor with it.
- 4
The digits of 16381 add up to 19, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 159 steps to reach 1.
16381 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 16382 |
| Euler totient φ(n) | 16380 |
| Square | 268337161 |
| Cube | 4395631034341 |
| Square root | 127.988281 |
| Digit sum / digital root | 19 / 1 |
| Collatz steps to 1 | 159 |
| Scientific notation | 1.6381 × |
16381 in other forms
| Form | Value |
|---|---|
| In words | sixteen thousand three hundred and eighty-one |
| Binary (base 2) | 11111111111101 |
| Octal (base 8) | 37775 |
| Hexadecimal (base 16) | 3FFD |
| Base 3 | 211110201 |
| As time | 16381 seconds = 4 h 33 min 1 s |
Is 16381 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 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 5) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 1) | 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 2) | 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 16381 a prime number?
Yes. 16381 is divisible only by 1 and itself.
What are the factors of 16381?
1, 16381.
What is 16381 in binary?
11111111111101 (hexadecimal 3FFD, octal 37775).
What is the square root of 16381?
About 127.9883.
Is 16381 divisible by 3?
No. Its digits add up to 19, which is not a multiple of 3.
What is special about the number 16381?
16381 is the 1900th prime number.