The number 21890
21890 is a composite number with 16 divisors. Its prime factorisation is 2 × 5 × 11 × 199. Divisors (16): 1, 2, 5, 10, 11, 22, 55, 110, 199, 398, 995, 1990, 2189, 4378, 10945, 21890.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21890 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21890 is composite. Its prime factorisation is
- 3
The divisors add up to 43200; without 21890 itself that is 21310, so 21890 is deficient (21310 is less than 21890). Euler's totient φ(21890) = 7920 numbers up to 21890 share no factor with it.
- 4
The digits of 21890 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 43 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21890 = 2 \times 5 \times 11 \times 199 \]
21890 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 43200 |
| Euler totient φ(n) | 7920 |
| Square | 479172100 |
| Cube | 10489077269000 |
| Square root | 147.952695 |
| Digit sum / digital root | 20 / 2 |
| Collatz steps to 1 | 43 |
| Scientific notation | 2.189 × |
21890 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand eight hundred and ninety |
| Binary (base 2) | 101010110000010 |
| Octal (base 8) | 52602 |
| Hexadecimal (base 16) | 5582 |
| Base 3 | 1010000202 |
| As time | 21890 seconds = 6 h 4 min 50 s |
Is 21890 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21890 ÷ 2 = 10945) | 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 (21890 ÷ 5 = 4378) | 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 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 2) | 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 (21890 ÷ 10 = 2189) | A number is divisible by 10 if the last digit is 0. |
| 11 | Yes (21890 ÷ 11 = 1990) | 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 21890 a prime number?
No. 21890 = 2 × 5 × 11 × 199, so it is divisible by 2.
What are the factors of 21890?
1, 2, 5, 10, 11, 22, 55, 110, 199, 398, 995, 1990, 2189, 4378, 10945, 21890.
What is 21890 in binary?
101010110000010 (hexadecimal 5582, octal 52602).
What is the square root of 21890?
About 147.9527.
Is 21890 divisible by 3?
No. Its digits add up to 20, which is not a multiple of 3.
What is special about the number 21890?
It is a composite number with 16 divisors.