The number 21940
21940 is a composite number with 12 divisors. Its prime factorisation is × 5 × 1097. Divisors (12): 1, 2, 4, 5, 10, 20, 1097, 2194, 4388, 5485, 10970, 21940.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21940 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21940 is composite. Its prime factorisation is
- 3
The divisors add up to 46116; without 21940 itself that is 24176, so 21940 is abundant (24176 is more than 21940). Euler's totient φ(21940) = 8768 numbers up to 21940 share no factor with it.
- 4
The digits of 21940 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 118 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21940 = 2^{2} \times 5 \times 1097 \]21940 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 46116 |
| Euler totient φ(n) | 8768 |
| Square | 481363600 |
| Cube | 10561117384000 |
| Square root | 148.121572 (= 2√5485) |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 118 |
| Scientific notation | 2.194 × |
21940 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand nine hundred and forty |
| Binary (base 2) | 101010110110100 |
| Octal (base 8) | 52664 |
| Hexadecimal (base 16) | 55B4 |
| Base 3 | 1010002121 |
| As time | 21940 seconds = 6 h 5 min 40 s |
Is 21940 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21940 ÷ 2 = 10970) | 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 | Yes (21940 ÷ 4 = 5485) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (21940 ÷ 5 = 4388) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 4) | 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 4) | 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 | Yes (21940 ÷ 10 = 2194) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 6) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 4) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21940 a prime number?
No. 21940 = × 5 × 1097, so it is divisible by 2.
What are the factors of 21940?
1, 2, 4, 5, 10, 20, 1097, 2194, 4388, 5485, 10970, 21940.
What is 21940 in binary?
101010110110100 (hexadecimal 55B4, octal 52664).
What is the square root of 21940?
About 148.1216, exactly 2√5485.
Is 21940 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 21940?
It is a composite number with 12 divisors.