The number 78401
78401 is the 7695th prime number. Its only divisors are 1 and 78401.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 78401: the 7695th prime number; a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
78401 is prime, so its only factors are 1 and 78401. It is the 7695th prime; the next prime is 78427 and the one before is 78367.
- 3
The divisors add up to 78402; without 78401 itself that is 1, so 78401 is deficient (1 is less than 78401). Euler's totient φ(78401) = 78400 numbers up to 78401 share no factor with it.
- 4
The digits of 78401 add up to 20, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 169 steps to reach 1.
78401 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 78402 |
| Euler totient φ(n) | 78400 |
| Square | 6146716801 |
| Cube | 481908743915201 |
| Square root | 280.001786 |
| Digit sum / digital root | 20 / 2 |
| Collatz steps to 1 | 169 |
| Scientific notation | 7.8401 × |
78401 in other forms
| Form | Value |
|---|---|
| In words | seventy-eight thousand four hundred and one |
| Binary (base 2) | 10011001001000001 |
| Octal (base 8) | 231101 |
| Hexadecimal (base 16) | 13241 |
| Base 3 | 10222112202 |
| As time | 78401 seconds = 21 h 46 min 41 s |
Is 78401 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 | No (remainder 1) | 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 2) | 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 4) | 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 78401 a prime number?
Yes. 78401 is divisible only by 1 and itself.
What are the factors of 78401?
1, 78401.
What is 78401 in binary?
10011001001000001 (hexadecimal 13241, octal 231101).
What is the square root of 78401?
About 280.0018.
Is 78401 divisible by 3?
No. Its digits add up to 20, which is not a multiple of 3.
What is special about the number 78401?
78401 is the 7695th prime number; a happy number: repeatedly adding the squares of its digits reaches 1.