The number 21998
21998 is a composite number with 8 divisors. Its prime factorisation is 2 × 17 × 647. Divisors (8): 1, 2, 17, 34, 647, 1294, 10999, 21998.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21998 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21998 is composite. Its prime factorisation is
- 3
The divisors add up to 34992; without 21998 itself that is 12994, so 21998 is deficient (12994 is less than 21998). Euler's totient φ(21998) = 10336 numbers up to 21998 share no factor with it.
- 4
The digits of 21998 add up to 29, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 69 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21998 = 2 \times 17 \times 647 \]
21998 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 34992 |
| Euler totient φ(n) | 10336 |
| Square | 483912004 |
| Cube | 10645096263992 |
| Square root | 148.317228 |
| Digit sum / digital root | 29 / 2 |
| Collatz steps to 1 | 69 |
| Scientific notation | 2.1998 × |
21998 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand nine hundred and ninety-eight |
| Binary (base 2) | 101010111101110 |
| Octal (base 8) | 52756 |
| Hexadecimal (base 16) | 55EE |
| Base 3 | 1010011202 |
| As time | 21998 seconds = 6 h 6 min 38 s |
Is 21998 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21998 ÷ 2 = 10999) | 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 | No (remainder 3) | 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 | No (remainder 8) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 9) | 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 21998 a prime number?
No. 21998 = 2 × 17 × 647, so it is divisible by 2.
What are the factors of 21998?
1, 2, 17, 34, 647, 1294, 10999, 21998.
What is 21998 in binary?
101010111101110 (hexadecimal 55EE, octal 52756).
What is the square root of 21998?
About 148.3172.
Is 21998 divisible by 3?
No. Its digits add up to 29, which is not a multiple of 3.
What is special about the number 21998?
It is a composite number with 8 divisors.