The number 21380
21380 is a composite number with 12 divisors. Its prime factorisation is × 5 × 1069. Divisors (12): 1, 2, 4, 5, 10, 20, 1069, 2138, 4276, 5345, 10690, 21380.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21380 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21380 is composite. Its prime factorisation is
- 3
The divisors add up to 44940; without 21380 itself that is 23560, so 21380 is abundant (23560 is more than 21380). Euler's totient φ(21380) = 8544 numbers up to 21380 share no factor with it.
- 4
The digits of 21380 add up to 14, and repeating that until one digit is left gives the digital root 5. The Collatz sequence (halve if even, else 3n+1) takes 162 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21380 = 2^{2} \times 5 \times 1069 \]21380 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 44940 |
| Euler totient φ(n) | 8544 |
| Square | 457104400 |
| Cube | 9772892072000 |
| Square root | 146.219014 (= 2√5345) |
| Digit sum / digital root | 14 / 5 |
| Collatz steps to 1 | 162 |
| Scientific notation | 2.138 × |
21380 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand three hundred and eighty |
| Binary (base 2) | 101001110000100 |
| Octal (base 8) | 51604 |
| Hexadecimal (base 16) | 5384 |
| Base 3 | 1002022212 |
| As time | 21380 seconds = 5 h 56 min 20 s |
Is 21380 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21380 ÷ 2 = 10690) | 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 | Yes (21380 ÷ 4 = 5345) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (21380 ÷ 5 = 4276) | 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 2) | 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 4) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 5) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (21380 ÷ 10 = 2138) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 7) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 8) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21380 a prime number?
No. 21380 = × 5 × 1069, so it is divisible by 2.
What are the factors of 21380?
1, 2, 4, 5, 10, 20, 1069, 2138, 4276, 5345, 10690, 21380.
What is 21380 in binary?
101001110000100 (hexadecimal 5384, octal 51604).
What is the square root of 21380?
About 146.2190, exactly 2√5345.
Is 21380 divisible by 3?
No. Its digits add up to 14, which is not a multiple of 3.
What is special about the number 21380?
It is a composite number with 12 divisors.