The number 21003
21003 is a composite number with 4 divisors. Its prime factorisation is 3 × 7001. Divisors (4): 1, 3, 7001, 21003.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21003: a semiprime: 3 × 7001, the product of two primes.
- 2
21003 is composite. Its prime factorisation is
- 3
The divisors add up to 28008; without 21003 itself that is 7005, so 21003 is deficient (7005 is less than 21003). Euler's totient φ(21003) = 14000 numbers up to 21003 share no factor with it.
- 4
The digits of 21003 add up to 6, and repeating that until one digit is left gives the digital root 6. The Collatz sequence (halve if even, else 3n+1) takes 131 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21003 = 3 \times 7001 \]
21003 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 28008 |
| Euler totient φ(n) | 14000 |
| Square | 441126009 |
| Cube | 9264969567027 |
| Square root | 144.924118 |
| Digit sum / digital root | 6 / 6 |
| Collatz steps to 1 | 131 |
| Scientific notation | 2.1003 × |
21003 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand and three |
| Binary (base 2) | 101001000001011 |
| Octal (base 8) | 51013 |
| Hexadecimal (base 16) | 520B |
| Base 3 | 1001210220 |
| As time | 21003 seconds = 5 h 50 min 3 s |
Is 21003 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 (21003 ÷ 3 = 7001) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 3) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 3) | 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 3) | 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 3) | 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 3) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 4) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21003 a prime number?
No. 21003 = 3 × 7001, so it is divisible by 3.
What are the factors of 21003?
1, 3, 7001, 21003.
What is 21003 in binary?
101001000001011 (hexadecimal 520B, octal 51013).
What is the square root of 21003?
About 144.9241.
Is 21003 divisible by 3?
Yes. Its digits add up to 6, a multiple of 3.
What is special about the number 21003?
21003 is a semiprime: 3 × 7001, the product of two primes.