The number 70821
70821 is a composite number with 16 divisors. Its prime factorisation is × 43 × 61. Divisors (16): 1, 3, 9, 27, 43, 61, 129, 183, 387, 549, 1161, 1647, 2623, 7869, 23607, 70821.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
70821 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
70821 is composite. Its prime factorisation is
- 3
The divisors add up to 109120; without 70821 itself that is 38299, so 70821 is deficient (38299 is less than 70821). Euler's totient φ(70821) = 45360 numbers up to 70821 share no factor with it.
- 4
The digits of 70821 add up to 18, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 81 steps to reach 1.
LaTeX source of the formulas on this page
\[ 70821 = 3^{3} \times 43 \times 61 \]70821 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 109120 |
| Euler totient φ(n) | 45360 |
| Square | 5015614041 |
| Cube | 355210801997661 |
| Square root | 266.122152 (= 3√7869) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 81 |
| Scientific notation | 7.0821 × |
70821 in other forms
| Form | Value |
|---|---|
| In words | seventy thousand eight hundred and twenty-one |
| Binary (base 2) | 10001010010100101 |
| Octal (base 8) | 212245 |
| Hexadecimal (base 16) | 114A5 |
| Base 3 | 10121011000 |
| As time | 70821 seconds = 19 h 40 min 21 s |
Is 70821 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | No (remainder 1) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (70821 ÷ 3 = 23607) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 1) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 1) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 3) | 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 5) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (70821 ÷ 9 = 7869) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 1) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 3) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 70821 a prime number?
No. 70821 = × 43 × 61, so it is divisible by 3.
What are the factors of 70821?
1, 3, 9, 27, 43, 61, 129, 183, 387, 549, 1161, 1647, 2623, 7869, 23607, 70821.
What is 70821 in binary?
10001010010100101 (hexadecimal 114A5, octal 212245).
What is the square root of 70821?
About 266.1222, exactly 3√7869.
Is 70821 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 70821?
It is a composite number with 16 divisors.