The number 21002
21002 is a composite number with 4 divisors. Its prime factorisation is 2 × 10501. Divisors (4): 1, 2, 10501, 21002.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21002: a semiprime: 2 × 10501, the product of two primes.
- 2
21002 is composite. Its prime factorisation is
- 3
The divisors add up to 31506; without 21002 itself that is 10504, so 21002 is deficient (10504 is less than 21002). Euler's totient φ(21002) = 10500 numbers up to 21002 share no factor with it.
- 4
The digits of 21002 add up to 5, and repeating that until one digit is left gives the digital root 5. The Collatz sequence (halve if even, else 3n+1) takes 30 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21002 = 2 \times 10501 \]
21002 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 31506 |
| Euler totient φ(n) | 10500 |
| Square | 441084004 |
| Cube | 9263646252008 |
| Square root | 144.920668 |
| Digit sum / digital root | 5 / 5 |
| Collatz steps to 1 | 30 |
| Scientific notation | 2.1002 × |
21002 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand and two |
| Binary (base 2) | 101001000001010 |
| Octal (base 8) | 51012 |
| Hexadecimal (base 16) | 520A |
| Base 3 | 1001210212 |
| As time | 21002 seconds = 5 h 50 min 2 s |
Is 21002 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21002 ÷ 2 = 10501) | 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 2) | 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 2) | 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 2) | 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 2) | 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 2) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21002 a prime number?
No. 21002 = 2 × 10501, so it is divisible by 2.
What are the factors of 21002?
1, 2, 10501, 21002.
What is 21002 in binary?
101001000001010 (hexadecimal 520A, octal 51012).
What is the square root of 21002?
About 144.9207.
Is 21002 divisible by 3?
No. Its digits add up to 5, which is not a multiple of 3.
What is special about the number 21002?
21002 is a semiprime: 2 × 10501, the product of two primes.