The number 20990
20990 is a composite number with 8 divisors. Its prime factorisation is 2 × 5 × 2099. Divisors (8): 1, 2, 5, 10, 2099, 4198, 10495, 20990.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
20990 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
20990 is composite. Its prime factorisation is
- 3
The divisors add up to 37800; without 20990 itself that is 16810, so 20990 is deficient (16810 is less than 20990). Euler's totient φ(20990) = 8392 numbers up to 20990 share no factor with it.
- 4
The digits of 20990 add up to 20, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 87 steps to reach 1.
LaTeX source of the formulas on this page
\[ 20990 = 2 \times 5 \times 2099 \]
20990 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 37800 |
| Euler totient φ(n) | 8392 |
| Square | 440580100 |
| Cube | 9247776299000 |
| Square root | 144.879260 |
| Digit sum / digital root | 20 / 2 |
| Collatz steps to 1 | 87 |
| Scientific notation | 2.099 × |
20990 in other forms
| Form | Value |
|---|---|
| In words | twenty thousand nine hundred and ninety |
| Binary (base 2) | 101000111111110 |
| Octal (base 8) | 50776 |
| Hexadecimal (base 16) | 51FE |
| Base 3 | 1001210102 |
| As time | 20990 seconds = 5 h 49 min 50 s |
Is 20990 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (20990 ÷ 2 = 10495) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | No (remainder 2) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 2) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (20990 ÷ 5 = 4198) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 2) | 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 6) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 2) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (20990 ÷ 10 = 2099) | 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 2) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 20990 a prime number?
No. 20990 = 2 × 5 × 2099, so it is divisible by 2.
What are the factors of 20990?
1, 2, 5, 10, 2099, 4198, 10495, 20990.
What is 20990 in binary?
101000111111110 (hexadecimal 51FE, octal 50776).
What is the square root of 20990?
About 144.8793.
Is 20990 divisible by 3?
No. Its digits add up to 20, which is not a multiple of 3.
What is special about the number 20990?
It is a composite number with 8 divisors.