The number 78787
78787 is a palindromic prime: it reads the same backwards and is prime, the 7727th prime number and a palindrome: it reads 78787 backwards too. Its only divisors are 1 and 78787.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 78787: a palindromic prime: it reads the same backwards and is prime; the 7727th prime number; a palindrome: it reads 78787 backwards too.
- 2
78787 is prime, so its only factors are 1 and 78787. It is the 7727th prime; the next prime is 78791 and the one before is 78781.
- 3
The divisors add up to 78788; without 78787 itself that is 1, so 78787 is deficient (1 is less than 78787). Euler's totient φ(78787) = 78786 numbers up to 78787 share no factor with it.
- 4
The digits of 78787 add up to 37, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 50 steps to reach 1.
78787 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 78788 |
| Euler totient φ(n) | 78786 |
| Square | 6207391369 |
| Cube | 489061743789403 |
| Square root | 280.690221 |
| Digit sum / digital root | 37 / 1 |
| Collatz steps to 1 | 50 |
| Scientific notation | 7.8787 × |
78787 in other forms
| Form | Value |
|---|---|
| In words | seventy-eight thousand seven hundred and eighty-seven |
| Binary (base 2) | 10011001111000011 |
| Octal (base 8) | 231703 |
| Hexadecimal (base 16) | 133C3 |
| Base 3 | 11000002001 |
| As time | 78787 seconds = 21 h 53 min 7 s |
Is 78787 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 2) | 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 1) | 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 5) | 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 78787 a prime number?
Yes. 78787 is divisible only by 1 and itself.
What are the factors of 78787?
1, 78787.
What is 78787 in binary?
10011001111000011 (hexadecimal 133C3, octal 231703).
What is the square root of 78787?
About 280.6902.
Is 78787 divisible by 3?
No. Its digits add up to 37, which is not a multiple of 3.
What is special about the number 78787?
78787 is a palindromic prime: it reads the same backwards and is prime; the 7727th prime number; a palindrome: it reads 78787 backwards too.