The number 21040
21040 is a composite number with 20 divisors. Its prime factorisation is × 5 × 263. Divisors (20): 1, 2, 4, 5, 8, 10, 16, 20, 40, 80, 263, 526, 1052, 1315, 2104, 2630 … 21040.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21040 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21040 is composite. Its prime factorisation is
- 3
The divisors add up to 49104; without 21040 itself that is 28064, so 21040 is abundant (28064 is more than 21040). Euler's totient φ(21040) = 8384 numbers up to 21040 share no factor with it.
- 4
The digits of 21040 add up to 7, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 56 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21040 = 2^{4} \times 5 \times 263 \]21040 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 20 |
| Sum of divisors | 49104 |
| Euler totient φ(n) | 8384 |
| Square | 442681600 |
| Cube | 9314020864000 |
| Square root | 145.051715 (= 4√1315) |
| Digit sum / digital root | 7 / 7 |
| Collatz steps to 1 | 56 |
| Scientific notation | 2.104 × |
21040 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand and forty |
| Binary (base 2) | 101001000110000 |
| Octal (base 8) | 51060 |
| Hexadecimal (base 16) | 5230 |
| Base 3 | 1001212021 |
| As time | 21040 seconds = 5 h 50 min 40 s |
Is 21040 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21040 ÷ 2 = 10520) | 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 (21040 ÷ 4 = 5260) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (21040 ÷ 5 = 4208) | 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 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 | Yes (21040 ÷ 8 = 2630) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 7) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (21040 ÷ 10 = 2104) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 8) | 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 21040 a prime number?
No. 21040 = × 5 × 263, so it is divisible by 2.
What are the factors of 21040?
1, 2, 4, 5, 8, 10, 16, 20, 40, 80, 263, 526, 1052, 1315, 2104, 2630, 4208, 5260, 10520, 21040.
What is 21040 in binary?
101001000110000 (hexadecimal 5230, octal 51060).
What is the square root of 21040?
About 145.0517, exactly 4√1315.
Is 21040 divisible by 3?
No. Its digits add up to 7, which is not a multiple of 3.
What is special about the number 21040?
It is a composite number with 20 divisors.