The number 51821
51821 is a composite number with 8 divisors. Its prime factorisation is 7 × 11 × 673. Divisors (8): 1, 7, 11, 77, 673, 4711, 7403, 51821.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
51821 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
51821 is composite. Its prime factorisation is
- 3
The divisors add up to 64704; without 51821 itself that is 12883, so 51821 is deficient (12883 is less than 51821). Euler's totient φ(51821) = 40320 numbers up to 51821 share no factor with it.
- 4
The digits of 51821 add up to 17, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 109 steps to reach 1.
LaTeX source of the formulas on this page
\[ 51821 = 7 \times 11 \times 673 \]
51821 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 64704 |
| Euler totient φ(n) | 40320 |
| Square | 2685416041 |
| Cube | 139160944660661 |
| Square root | 227.642263 |
| Digit sum / digital root | 17 / 8 |
| Collatz steps to 1 | 109 |
| Scientific notation | 5.1821 × |
51821 in other forms
| Form | Value |
|---|---|
| In words | fifty-one thousand eight hundred and twenty-one |
| Binary (base 2) | 1100101001101101 |
| Octal (base 8) | 145155 |
| Hexadecimal (base 16) | CA6D |
| Base 3 | 2122002022 |
| As time | 51821 seconds = 14 h 23 min 41 s |
Is 51821 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 2) | 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 5) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | Yes (51821 ÷ 7 = 7403) | 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 8) | 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 | Yes (51821 ÷ 11 = 4711) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 5) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 51821 a prime number?
No. 51821 = 7 × 11 × 673, so it is divisible by 7.
What are the factors of 51821?
1, 7, 11, 77, 673, 4711, 7403, 51821.
What is 51821 in binary?
1100101001101101 (hexadecimal CA6D, octal 145155).
What is the square root of 51821?
About 227.6423.
Is 51821 divisible by 3?
No. Its digits add up to 17, which is not a multiple of 3.
What is special about the number 51821?
It is a composite number with 8 divisors.