The number 787
787 is a palindromic prime: it reads the same backwards and is prime, the 138th prime number and a palindrome: it reads 787 backwards too. Its only divisors are 1 and 787.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 787: a palindromic prime: it reads the same backwards and is prime; the 138th prime number; a palindrome: it reads 787 backwards too.
- 2
787 is prime, so its only factors are 1 and 787. It is the 138th prime; the next prime is 797 and the one before is 773.
- 3
The divisors add up to 788; without 787 itself that is 1, so 787 is deficient (1 is less than 787). Euler's totient φ(787) = 786 numbers up to 787 share no factor with it.
- 4
The digits of 787 add up to 22, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 59 steps to reach 1.
787 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 788 |
| Euler totient φ(n) | 786 |
| Square | 619369 |
| Cube | 487443403 |
| Square root | 28.053520 |
| Digit sum / digital root | 22 / 4 |
| Collatz steps to 1 | 59 |
| Scientific notation | 7.87 × |
787 in other forms
| Form | Value |
|---|---|
| In words | seven hundred and eighty-seven |
| Roman numerals | DCCLXXXVII |
| Binary (base 2) | 1100010011 |
| Octal (base 8) | 1423 |
| Hexadecimal (base 16) | 313 |
| Base 3 | 1002011 |
| As time | 787 seconds = 13 min 7 s |
Is 787 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 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 1) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 3) | 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 3) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 4) | 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 | No (remainder 6) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 7) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 787 a prime number?
Yes. 787 is divisible only by 1 and itself.
What are the factors of 787?
1, 787.
What is 787 in binary?
1100010011 (hexadecimal 313, octal 1423).
What is the square root of 787?
About 28.0535.
What is 787 in Roman numerals?
DCCLXXXVII.
Is 787 divisible by 3?
No. Its digits add up to 22, which is not a multiple of 3.
What is special about the number 787?
787 is a palindromic prime: it reads the same backwards and is prime; the 138th prime number; a palindrome: it reads 787 backwards too.