The number 21388
21388 is a composite number with 6 divisors. Its prime factorisation is × 5347. Divisors (6): 1, 2, 4, 5347, 10694, 21388.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21388 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21388 is composite. Its prime factorisation is
- 3
The divisors add up to 37436; without 21388 itself that is 16048, so 21388 is deficient (16048 is less than 21388). Euler's totient φ(21388) = 10692 numbers up to 21388 share no factor with it.
- 4
The digits of 21388 add up to 22, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 118 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21388 = 2^{2} \times 5347 \]21388 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 6 |
| Sum of divisors | 37436 |
| Euler totient φ(n) | 10692 |
| Square | 457446544 |
| Cube | 9783866683072 |
| Square root | 146.246367 (= 2√5347) |
| Digit sum / digital root | 22 / 4 |
| Collatz steps to 1 | 118 |
| Scientific notation | 2.1388 × |
21388 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand three hundred and eighty-eight |
| Binary (base 2) | 101001110001100 |
| Octal (base 8) | 51614 |
| Hexadecimal (base 16) | 538C |
| Base 3 | 1002100011 |
| As time | 21388 seconds = 5 h 56 min 28 s |
Is 21388 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21388 ÷ 2 = 10694) | 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 | Yes (21388 ÷ 4 = 5347) | 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 4) | 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 4) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 4) | 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 4) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 4) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21388 a prime number?
No. 21388 = × 5347, so it is divisible by 2.
What are the factors of 21388?
1, 2, 4, 5347, 10694, 21388.
What is 21388 in binary?
101001110001100 (hexadecimal 538C, octal 51614).
What is the square root of 21388?
About 146.2464, exactly 2√5347.
Is 21388 divisible by 3?
No. Its digits add up to 22, which is not a multiple of 3.
What is special about the number 21388?
It is a composite number with 6 divisors.