The number 76721
76721 is a composite number with 4 divisors. Its prime factorisation is 17 × 4513. Divisors (4): 1, 17, 4513, 76721.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 76721: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 17 × 4513, the product of two primes.
- 2
76721 is composite. Its prime factorisation is
- 3
The divisors add up to 81252; without 76721 itself that is 4531, so 76721 is deficient (4531 is less than 76721). Euler's totient φ(76721) = 72192 numbers up to 76721 share no factor with it.
- 4
The digits of 76721 add up to 23, and repeating that until one digit is left gives the digital root 5. The Collatz sequence (halve if even, else 3n+1) takes 169 steps to reach 1.
LaTeX source of the formulas on this page
\[ 76721 = 17 \times 4513 \]
76721 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 81252 |
| Euler totient φ(n) | 72192 |
| Square | 5886111841 |
| Cube | 451588386553361 |
| Square root | 276.985559 |
| Digit sum / digital root | 23 / 5 |
| Collatz steps to 1 | 169 |
| Scientific notation | 7.6721 × |
76721 in other forms
| Form | Value |
|---|---|
| In words | seventy-six thousand seven hundred and twenty-one |
| Binary (base 2) | 10010101110110001 |
| Octal (base 8) | 225661 |
| Hexadecimal (base 16) | 12BB1 |
| Base 3 | 10220020112 |
| As time | 76721 seconds = 21 h 18 min 41 s |
Is 76721 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 5) | 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 7) | 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 76721 a prime number?
No. 76721 = 17 × 4513, so it is divisible by 17.
What are the factors of 76721?
1, 17, 4513, 76721.
What is 76721 in binary?
10010101110110001 (hexadecimal 12BB1, octal 225661).
What is the square root of 76721?
About 276.9856.
Is 76721 divisible by 3?
No. Its digits add up to 23, which is not a multiple of 3.
What is special about the number 76721?
76721 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 17 × 4513, the product of two primes.