The number 77421
77421 is a triangular number: 1 + 2 + … + 393 = 77421. Its prime factorisation is 3 × 131 × 197. Divisors (8): 1, 3, 131, 197, 393, 591, 25807, 77421.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 77421: a triangular number: 1 + 2 + … + 393 = 77421.
- 2
77421 is composite. Its prime factorisation is
- 3
The divisors add up to 104544; without 77421 itself that is 27123, so 77421 is deficient (27123 is less than 77421). Euler's totient φ(77421) = 50960 numbers up to 77421 share no factor with it.
- 4
The digits of 77421 add up to 21, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 125 steps to reach 1.
LaTeX source of the formulas on this page
\[ 77421 = 3 \times 131 \times 197 \]
77421 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 104544 |
| Euler totient φ(n) | 50960 |
| Square | 5994011241 |
| Cube | 464062344289461 |
| Square root | 278.246294 |
| Digit sum / digital root | 21 / 3 |
| Collatz steps to 1 | 125 |
| Scientific notation | 7.7421 × |
77421 in other forms
| Form | Value |
|---|---|
| In words | seventy-seven thousand four hundred and twenty-one |
| Binary (base 2) | 10010111001101101 |
| Octal (base 8) | 227155 |
| Hexadecimal (base 16) | 12E6D |
| Base 3 | 10221012110 |
| As time | 77421 seconds = 21 h 30 min 21 s |
Is 77421 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 | Yes (77421 ÷ 3 = 25807) | 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 3) | 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 3) | 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 3) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 77421 a prime number?
No. 77421 = 3 × 131 × 197, so it is divisible by 3.
What are the factors of 77421?
1, 3, 131, 197, 393, 591, 25807, 77421.
What is 77421 in binary?
10010111001101101 (hexadecimal 12E6D, octal 227155).
What is the square root of 77421?
About 278.2463.
Is 77421 divisible by 3?
Yes. Its digits add up to 21, a multiple of 3.
What is special about the number 77421?
77421 is a triangular number: 1 + 2 + … + 393 = 77421.