The number 80821
80821 is a composite number with 4 divisors. Its prime factorisation is 13 × 6217. Divisors (4): 1, 13, 6217, 80821.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 80821: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 13 × 6217, the product of two primes.
- 2
80821 is composite. Its prime factorisation is
- 3
The divisors add up to 87052; without 80821 itself that is 6231, so 80821 is deficient (6231 is less than 80821). Euler's totient φ(80821) = 74592 numbers up to 80821 share no factor with it.
- 4
The digits of 80821 add up to 19, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 89 steps to reach 1.
LaTeX source of the formulas on this page
\[ 80821 = 13 \times 6217 \]
80821 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 87052 |
| Euler totient φ(n) | 74592 |
| Square | 6532034041 |
| Cube | 527925523227661 |
| Square root | 284.290345 |
| Digit sum / digital root | 19 / 1 |
| Collatz steps to 1 | 89 |
| Scientific notation | 8.0821 × |
80821 in other forms
| Form | Value |
|---|---|
| In words | eighty thousand eight hundred and twenty-one |
| Binary (base 2) | 10011101110110101 |
| Octal (base 8) | 235665 |
| Hexadecimal (base 16) | 13BB5 |
| Base 3 | 11002212101 |
| As time | 80821 seconds = 22 h 27 min 1 s |
Is 80821 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 | No (remainder 1) | 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 1) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 6) | 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 | No (remainder 1) | 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 4) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 1) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 80821 a prime number?
No. 80821 = 13 × 6217, so it is divisible by 13.
What are the factors of 80821?
1, 13, 6217, 80821.
What is 80821 in binary?
10011101110110101 (hexadecimal 13BB5, octal 235665).
What is the square root of 80821?
About 284.2903.
Is 80821 divisible by 3?
No. Its digits add up to 19, which is not a multiple of 3.
What is special about the number 80821?
80821 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 13 × 6217, the product of two primes.