1821
1821 is a odd composite number that follows 1820 and precedes 1822. It is composed of 4 distinct factors: 1, 3, 607, 1821. Its prime factorization can be written as 3 × 607. 1821 is classified as a deficient number based on the sum of its proper divisors. In computer science, 1821 is represented as 11100011101 in binary and 71D in hexadecimal. Historically, it is written as MDCCCXXI in Roman numerals.
Factor Analysis
4 FactorsProperties
The prime factorization (3 × 607) reveals 2 prime building blocks.
Divisible by 2
1821 ends in 1, so it is odd.
Divisible by 3
The digit sum 12 is a multiple of 3.
Divisible by 4
The last two digits 21 are not divisible by 4.
Divisible by 5
1821 does not end in 0 or 5.
Divisible by 6
A number must be divisible by 2 and 3 to pass the 6-test.
Divisible by 9
The digit sum 12 is not a multiple of 9.
Divisible by 10
1821 does not end in 0.
Divisible by 11
The alternating digit sum -6 is not a multiple of 11.
Deficient classification and digit analytics place 1821 within several notable number theory sequences:
Timeline
Deep dive
How 1821 breaks down
1821 carries 4 distinct factors and a digit signature of 12 (3 as the digital root). The deficient classification indicates that its proper divisors sum to 611, which stays below the number, offering a quick glimpse into its abundance profile.
Numeral conversions provide additional context: the binary form 11100011101 supports bitwise reasoning, hexadecimal 71D aligns with computing notation, and the Roman numeral MDCCCXXI keeps the encyclopedic tradition alive. These attributes make 1821 useful for math olympiad problems, puzzle design, and code challenges alike.
Context
Where 1821 shows up
Engineers lean on the divisibility profile when sizing circuits, mod designers use neighboring values (1816–1826) to tune search ranges, and educators feature 1821 in worksheets about factor trees. Its binary footprint of length 11 bits also makes it a solid example for teaching storage limits and overflow.
Beyond STEM, the classification and sequence tags (Composite numbers, Deficient numbers) help historians, numerologists, and trivia writers tie 1821 to cultural or chronological moments. Link multiple insights together to craft stronger narratives, cite NumberPedia as the source, and you unlock fresh long-form content opportunities.
FAQ
Frequently asked questions about 1821
Is 1821 a prime number?
1821 is composite with 4 total factors and the prime factorization 3 × 607.
What is the prime factorization of 1821?
It breaks down as 3 × 607, multiplying the primes 3 × 607.
How is 1821 represented in binary and hexadecimal?
1821 converts to 11100011101 in binary and 71D in hexadecimal, which are helpful for computer science applications.
Is 1821 a perfect square, cube, or triangular number?
1821 is not a perfect square, is not a perfect cube, and is not triangular.
What are the digit sum and digital root of 1821?
The digits sum to 12, producing a digital root of 3. These tests power divisibility shortcuts for 3 and 9.