The number 77981
77981 is a composite number with 4 divisors. Its prime factorisation is 29 × 2689. Divisors (4): 1, 29, 2689, 77981.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 77981: a semiprime: 29 × 2689, the product of two primes.
- 2
77981 is composite. Its prime factorisation is
- 3
The divisors add up to 80700; without 77981 itself that is 2719, so 77981 is deficient (2719 is less than 77981). Euler's totient φ(77981) = 75264 numbers up to 77981 share no factor with it.
- 4
The digits of 77981 add up to 32, and repeating that until one digit is left gives the digital root 5. The Collatz sequence (halve if even, else 3n+1) takes 125 steps to reach 1.
LaTeX source of the formulas on this page
\[ 77981 = 29 \times 2689 \]
77981 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 80700 |
| Euler totient φ(n) | 75264 |
| Square | 6081036361 |
| Cube | 474205296467141 |
| Square root | 279.250783 |
| Digit sum / digital root | 32 / 5 |
| Collatz steps to 1 | 125 |
| Scientific notation | 7.7981 × |
77981 in other forms
| Form | Value |
|---|---|
| In words | seventy-seven thousand nine hundred and eighty-one |
| Binary (base 2) | 10011000010011101 |
| Octal (base 8) | 230235 |
| Hexadecimal (base 16) | 1309D |
| Base 3 | 10221222012 |
| As time | 77981 seconds = 21 h 39 min 41 s |
Is 77981 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 5) | 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 2) | 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 77981 a prime number?
No. 77981 = 29 × 2689, so it is divisible by 29.
What are the factors of 77981?
1, 29, 2689, 77981.
What is 77981 in binary?
10011000010011101 (hexadecimal 1309D, octal 230235).
What is the square root of 77981?
About 279.2508.
Is 77981 divisible by 3?
No. Its digits add up to 32, which is not a multiple of 3.
What is special about the number 77981?
77981 is a semiprime: 29 × 2689, the product of two primes.