Number reference
210 explained.
210: two hundred ten, composite, triangular number; factors, prime factorization, roots, binary, hexadecimal, and digit properties.
Identity and representations
- Written form
- two hundred ten
- Classification
- composite
- Factors
- 1, 2, 3, 5, 6, 7, 10, 14, 15, 21, 30, 35, 42, 70, 105, 210
- Prime factorization
- 2 × 3 × 5 × 7
- Square root
- 14.491377
- Cube root
- 5.943922
- Binary
- 11010010
- Octal
- 322
- Hexadecimal
- D2
- Roman numeral
- CCX
- Digit sum
- 3
- Digital root
- 3
What makes 210 notable
- Triangular number. 210 is the 20th triangular number: it is the sum 1 + 2 + … + 20, the count of items in a triangle with 20 rows.
210 in everyday use
Two hundred ten is the product of the first four primes, 2 × 3 × 5 × 7, which makes it the smallest number divisible by every prime below 10 and the fourth primorial. That structure gives it sixteen divisors and makes it the modulus in the classic wheel for sieving primes: after 210, the pattern of which numbers can be prime repeats. Working only with numbers coprime to 210 discards more than three quarters of all candidates before any real testing begins.
It is also a triangular number, the sum of the whole numbers from 1 to 20, and a pentagonal number, and it is pronic, being 14 × 15. Apart from 1, it is the smallest number that is both triangular and pentagonal; the next is 40,755. It is 11010010 in binary and D2 in hexadecimal, its digit sum is 3, and it is the number of degrees in seven twelfths of a full turn, the direction a clock hand points at seven o'clock.
Nearby numbers
How to read this page
The factor list shows every way 210 splits into equal whole-number groups — 16 divisors in total. The prime factorisation is the compact form of that same information, and the base conversions restate 210 for contexts that do not use decimal.
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