The number 21777
21777 is a composite number with 16 divisors. Its prime factorisation is 3 × 7 × 17 × 61. Divisors (16): 1, 3, 7, 17, 21, 51, 61, 119, 183, 357, 427, 1037, 1281, 3111, 7259, 21777.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21777 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21777 is composite. Its prime factorisation is
- 3
The divisors add up to 35712; without 21777 itself that is 13935, so 21777 is deficient (13935 is less than 21777). Euler's totient φ(21777) = 11520 numbers up to 21777 share no factor with it.
- 4
The digits of 21777 add up to 24, and repeating that until one digit is left gives the digital root 6. The Collatz sequence (halve if even, else 3n+1) takes 69 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21777 = 3 \times 7 \times 17 \times 61 \]
21777 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 35712 |
| Euler totient φ(n) | 11520 |
| Square | 474237729 |
| Cube | 10327475024433 |
| Square root | 147.570322 |
| Digit sum / digital root | 24 / 6 |
| Collatz steps to 1 | 69 |
| Scientific notation | 2.1777 × |
21777 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand seven hundred and seventy-seven |
| Binary (base 2) | 101010100010001 |
| Octal (base 8) | 52421 |
| Hexadecimal (base 16) | 5511 |
| Base 3 | 1002212120 |
| As time | 21777 seconds = 6 h 2 min 57 s |
Is 21777 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 (21777 ÷ 3 = 7259) | 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 2) | 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 | Yes (21777 ÷ 7 = 3111) | 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 6) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 7) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 8) | 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 21777 a prime number?
No. 21777 = 3 × 7 × 17 × 61, so it is divisible by 3.
What are the factors of 21777?
1, 3, 7, 17, 21, 51, 61, 119, 183, 357, 427, 1037, 1281, 3111, 7259, 21777.
What is 21777 in binary?
101010100010001 (hexadecimal 5511, octal 52421).
What is the square root of 21777?
About 147.5703.
Is 21777 divisible by 3?
Yes. Its digits add up to 24, a multiple of 3.
What is special about the number 21777?
It is a composite number with 16 divisors.