The number 79
79 is the 22nd prime number. Its only divisors are 1 and 79.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 79: the 22nd prime number; a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
79 is prime, so its only factors are 1 and 79. It is the 22nd prime; the next prime is 83 and the one before is 73.
- 3
The divisors add up to 80; without 79 itself that is 1, so 79 is deficient (1 is less than 79). Euler's totient φ(79) = 78 numbers up to 79 share no factor with it.
- 4
The digits of 79 add up to 16, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 35 steps to reach 1.
79 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 80 |
| Euler totient φ(n) | 78 |
| Square | 6241 |
| Cube | 493039 |
| Square root | 8.888194 |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 35 |
| Scientific notation | 7.9 × |
79 in other forms
| Form | Value |
|---|---|
| In words | seventy-nine |
| Roman numerals | LXXIX |
| Binary (base 2) | 1001111 |
| Octal (base 8) | 117 |
| Hexadecimal (base 16) | 4F |
| Base 3 | 2221 |
| As time | 79 seconds = 1 min 19 s |
Is 79 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 4) | 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 7) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 7) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 9) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 2) | 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 79 a prime number?
Yes. 79 is divisible only by 1 and itself.
What are the factors of 79?
1, 79.
What is 79 in binary?
1001111 (hexadecimal 4F, octal 117).
What is the square root of 79?
About 8.8882.
What is 79 in Roman numerals?
LXXIX.
Is 79 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 79?
79 is the 22nd prime number; a happy number: repeatedly adding the squares of its digits reaches 1.