The number 21138
21138 is a composite number with 16 divisors. Its prime factorisation is 2 × 3 × 13 × 271. Divisors (16): 1, 2, 3, 6, 13, 26, 39, 78, 271, 542, 813, 1626, 3523, 7046, 10569, 21138.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21138: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
21138 is composite. Its prime factorisation is
- 3
The divisors add up to 45696; without 21138 itself that is 24558, so 21138 is abundant (24558 is more than 21138). Euler's totient φ(21138) = 6480 numbers up to 21138 share no factor with it.
- 4
The digits of 21138 add up to 15, and repeating that until one digit is left gives the digital root 6. The Collatz sequence (halve if even, else 3n+1) takes 56 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21138 = 2 \times 3 \times 13 \times 271 \]
21138 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 45696 |
| Euler totient φ(n) | 6480 |
| Square | 446815044 |
| Cube | 9444776400072 |
| Square root | 145.389133 |
| Digit sum / digital root | 15 / 6 |
| Collatz steps to 1 | 56 |
| Scientific notation | 2.1138 × |
21138 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand one hundred and thirty-eight |
| Binary (base 2) | 101001010010010 |
| Octal (base 8) | 51222 |
| Hexadecimal (base 16) | 5292 |
| Base 3 | 1001222220 |
| As time | 21138 seconds = 5 h 52 min 18 s |
Is 21138 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21138 ÷ 2 = 10569) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21138 ÷ 3 = 7046) | 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 | Yes (21138 ÷ 6 = 3523) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 5) | 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 6) | 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 7) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 6) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21138 a prime number?
No. 21138 = 2 × 3 × 13 × 271, so it is divisible by 2.
What are the factors of 21138?
1, 2, 3, 6, 13, 26, 39, 78, 271, 542, 813, 1626, 3523, 7046, 10569, 21138.
What is 21138 in binary?
101001010010010 (hexadecimal 5292, octal 51222).
What is the square root of 21138?
About 145.3891.
Is 21138 divisible by 3?
Yes. Its digits add up to 15, a multiple of 3.
What is special about the number 21138?
21138 is a happy number: repeatedly adding the squares of its digits reaches 1.