The number 16981
16981 is a twin prime (16979 and 16981 are both prime) and the 1958th prime number. Its only divisors are 1 and 16981.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 16981: a twin prime (16979 and 16981 are both prime); the 1958th prime number.
- 2
16981 is prime, so its only factors are 1 and 16981. It is the 1958th prime; the next prime is 16987 and the one before is 16979.
- 3
The divisors add up to 16982; without 16981 itself that is 1, so 16981 is deficient (1 is less than 16981). Euler's totient φ(16981) = 16980 numbers up to 16981 share no factor with it.
- 4
The digits of 16981 add up to 25, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 128 steps to reach 1.
16981 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 16982 |
| Euler totient φ(n) | 16980 |
| Square | 288354361 |
| Cube | 4896545404141 |
| Square root | 130.311166 |
| Digit sum / digital root | 25 / 7 |
| Collatz steps to 1 | 128 |
| Scientific notation | 1.6981 × |
16981 in other forms
| Form | Value |
|---|---|
| In words | sixteen thousand nine hundred and eighty-one |
| Binary (base 2) | 100001001010101 |
| Octal (base 8) | 41125 |
| Hexadecimal (base 16) | 4255 |
| Base 3 | 212021221 |
| As time | 16981 seconds = 4 h 43 min 1 s |
Is 16981 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 6) | 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 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 8) | 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 16981 a prime number?
Yes. 16981 is divisible only by 1 and itself.
What are the factors of 16981?
1, 16981.
What is 16981 in binary?
100001001010101 (hexadecimal 4255, octal 41125).
What is the square root of 16981?
About 130.3112.
Is 16981 divisible by 3?
No. Its digits add up to 25, which is not a multiple of 3.
What is special about the number 16981?
16981 is a twin prime (16979 and 16981 are both prime); the 1958th prime number.