The number 1287
1287 is a composite number with 12 divisors. Its prime factorisation is × 11 × 13. Divisors (12): 1, 3, 9, 11, 13, 33, 39, 99, 117, 143, 429, 1287.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
1287 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
1287 is composite. Its prime factorisation is
- 3
The divisors add up to 2184; without 1287 itself that is 897, so 1287 is deficient (897 is less than 1287). Euler's totient φ(1287) = 720 numbers up to 1287 share no factor with it.
- 4
The digits of 1287 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 145 steps to reach 1.
LaTeX source of the formulas on this page
\[ 1287 = 3^{2} \times 11 \times 13 \]1287 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 2184 |
| Euler totient φ(n) | 720 |
| Square | 1656369 |
| Cube | 2131746903 |
| Square root | 35.874782 (= 3√143) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 145 |
| Scientific notation | 1.287 × |
1287 in other forms
| Form | Value |
|---|---|
| In words | one thousand two hundred and eighty-seven |
| Roman numerals | MCCLXXXVII |
| Binary (base 2) | 10100000111 |
| Octal (base 8) | 2407 |
| Hexadecimal (base 16) | 507 |
| Base 3 | 1202200 |
| As time | 1287 seconds = 21 min 27 s |
Is 1287 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 (1287 ÷ 3 = 429) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 3) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 2) | 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 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 7) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (1287 ÷ 9 = 143) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 7) | A number is divisible by 10 if the last digit is 0. |
| 11 | Yes (1287 ÷ 11 = 117) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 1287 a prime number?
No. 1287 = × 11 × 13, so it is divisible by 3.
What are the factors of 1287?
1, 3, 9, 11, 13, 33, 39, 99, 117, 143, 429, 1287.
What is 1287 in binary?
10100000111 (hexadecimal 507, octal 2407).
What is the square root of 1287?
About 35.8748, exactly 3√143.
What is 1287 in Roman numerals?
MCCLXXXVII.
Is 1287 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 1287?
It is a composite number with 12 divisors.