The number 51681
51681 is a triangular number: 1 + 2 + … + 321 = 51681. Its prime factorisation is 3 × 7 × 23 × 107. Divisors (16): 1, 3, 7, 21, 23, 69, 107, 161, 321, 483, 749, 2247, 2461, 7383, 17227, 51681.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 51681: a triangular number: 1 + 2 + … + 321 = 51681; a Harshad number: divisible by its digit sum 21.
- 2
51681 is composite. Its prime factorisation is
- 3
The divisors add up to 82944; without 51681 itself that is 31263, so 51681 is deficient (31263 is less than 51681). Euler's totient φ(51681) = 27984 numbers up to 51681 share no factor with it.
- 4
The digits of 51681 add up to 21, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 171 steps to reach 1.
LaTeX source of the formulas on this page
\[ 51681 = 3 \times 7 \times 23 \times 107 \]
51681 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 82944 |
| Euler totient φ(n) | 27984 |
| Square | 2670925761 |
| Cube | 138036114254241 |
| Square root | 227.334555 |
| Digit sum / digital root | 21 / 3 |
| Collatz steps to 1 | 171 |
| Scientific notation | 5.1681 × |
51681 in other forms
| Form | Value |
|---|---|
| In words | fifty-one thousand six hundred and eighty-one |
| Binary (base 2) | 1100100111100001 |
| Octal (base 8) | 144741 |
| Hexadecimal (base 16) | C9E1 |
| Base 3 | 2121220010 |
| As time | 51681 seconds = 14 h 21 min 21 s |
Is 51681 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 (51681 ÷ 3 = 17227) | 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 | Yes (51681 ÷ 7 = 7383) | 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 3) | 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 51681 a prime number?
No. 51681 = 3 × 7 × 23 × 107, so it is divisible by 3.
What are the factors of 51681?
1, 3, 7, 21, 23, 69, 107, 161, 321, 483, 749, 2247, 2461, 7383, 17227, 51681.
What is 51681 in binary?
1100100111100001 (hexadecimal C9E1, octal 144741).
What is the square root of 51681?
About 227.3346.
Is 51681 divisible by 3?
Yes. Its digits add up to 21, a multiple of 3.
What is special about the number 51681?
51681 is a triangular number: 1 + 2 + … + 321 = 51681; a Harshad number: divisible by its digit sum 21.