The number 78121
78121 is the 7671st prime number. Its only divisors are 1 and 78121.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 78121: the 7671st prime number.
- 2
78121 is prime, so its only factors are 1 and 78121. It is the 7671st prime; the next prime is 78137 and the one before is 78101.
- 3
The divisors add up to 78122; without 78121 itself that is 1, so 78121 is deficient (1 is less than 78121). Euler's totient φ(78121) = 78120 numbers up to 78121 share no factor with it.
- 4
The digits of 78121 add up to 19, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 156 steps to reach 1.
78121 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 78122 |
| Euler totient φ(n) | 78120 |
| Square | 6102890641 |
| Cube | 476763919765561 |
| Square root | 279.501342 |
| Digit sum / digital root | 19 / 1 |
| Collatz steps to 1 | 156 |
| Scientific notation | 7.8121 × |
78121 in other forms
| Form | Value |
|---|---|
| In words | seventy-eight thousand one hundred and twenty-one |
| Binary (base 2) | 10011000100101001 |
| Octal (base 8) | 230451 |
| Hexadecimal (base 16) | 13129 |
| Base 3 | 10222011101 |
| As time | 78121 seconds = 21 h 42 min 1 s |
Is 78121 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 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 1) | 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 1) | 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 10) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 1) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 78121 a prime number?
Yes. 78121 is divisible only by 1 and itself.
What are the factors of 78121?
1, 78121.
What is 78121 in binary?
10011000100101001 (hexadecimal 13129, octal 230451).
What is the square root of 78121?
About 279.5013.
Is 78121 divisible by 3?
No. Its digits add up to 19, which is not a multiple of 3.
What is special about the number 78121?
78121 is the 7671st prime number.