The number 19981
19981 is a composite number with 8 divisors. Its prime factorisation is 13 × 29 × 53. Divisors (8): 1, 13, 29, 53, 377, 689, 1537, 19981.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
19981 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
19981 is composite. Its prime factorisation is
- 3
The divisors add up to 22680; without 19981 itself that is 2699, so 19981 is deficient (2699 is less than 19981). Euler's totient φ(19981) = 17472 numbers up to 19981 share no factor with it.
- 4
The digits of 19981 add up to 28, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 92 steps to reach 1.
LaTeX source of the formulas on this page
\[ 19981 = 13 \times 29 \times 53 \]
19981 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 22680 |
| Euler totient φ(n) | 17472 |
| Square | 399240361 |
| Cube | 7977221653141 |
| Square root | 141.354165 |
| Digit sum / digital root | 28 / 1 |
| Collatz steps to 1 | 92 |
| Scientific notation | 1.9981 × |
19981 in other forms
| Form | Value |
|---|---|
| In words | nineteen thousand nine hundred and eighty-one |
| Binary (base 2) | 100111000001101 |
| Octal (base 8) | 47015 |
| Hexadecimal (base 16) | 4E0D |
| Base 3 | 1000102001 |
| As time | 19981 seconds = 5 h 33 min 1 s |
Is 19981 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 3) | 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 5) | 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 19981 a prime number?
No. 19981 = 13 × 29 × 53, so it is divisible by 13.
What are the factors of 19981?
1, 13, 29, 53, 377, 689, 1537, 19981.
What is 19981 in binary?
100111000001101 (hexadecimal 4E0D, octal 47015).
What is the square root of 19981?
About 141.3542.
Is 19981 divisible by 3?
No. Its digits add up to 28, which is not a multiple of 3.
What is special about the number 19981?
It is a composite number with 8 divisors.