The number 21100
21100 is a composite number with 18 divisors. Its prime factorisation is × × 211. Divisors (18): 1, 2, 4, 5, 10, 20, 25, 50, 100, 211, 422, 844, 1055, 2110, 4220, 5275 … 21100.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21100: a Harshad number: divisible by its digit sum 4.
- 2
21100 is composite. Its prime factorisation is
- 3
The divisors add up to 46004; without 21100 itself that is 24904, so 21100 is abundant (24904 is more than 21100). Euler's totient φ(21100) = 8400 numbers up to 21100 share no factor with it.
- 4
The digits of 21100 add up to 4, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 105 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21100 = 2^{2} \times 5^{2} \times 211 \]21100 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 18 |
| Sum of divisors | 46004 |
| Euler totient φ(n) | 8400 |
| Square | 445210000 |
| Cube | 9393931000000 |
| Square root | 145.258390 (= 10√211) |
| Digit sum / digital root | 4 / 4 |
| Collatz steps to 1 | 105 |
| Scientific notation | 2.11 × |
21100 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand one hundred |
| Binary (base 2) | 101001001101100 |
| Octal (base 8) | 51154 |
| Hexadecimal (base 16) | 526C |
| Base 3 | 1001221111 |
| As time | 21100 seconds = 5 h 51 min 40 s |
Is 21100 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21100 ÷ 2 = 10550) | 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 (21100 ÷ 4 = 5275) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (21100 ÷ 5 = 4220) | 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 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 4) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (21100 ÷ 10 = 2110) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 2) | 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 21100 a prime number?
No. 21100 = × × 211, so it is divisible by 2.
What are the factors of 21100?
1, 2, 4, 5, 10, 20, 25, 50, 100, 211, 422, 844, 1055, 2110, 4220, 5275, 10550, 21100.
What is 21100 in binary?
101001001101100 (hexadecimal 526C, octal 51154).
What is the square root of 21100?
About 145.2584, exactly 10√211.
Is 21100 divisible by 3?
No. Its digits add up to 4, which is not a multiple of 3.
What is special about the number 21100?
21100 is a Harshad number: divisible by its digit sum 4.