221
221 is a odd composite number that follows 220 and precedes 222. It is composed of 4 distinct factors: 1, 13, 17, 221. Its prime factorization can be written as 13 × 17. 221 is classified as a deficient number based on the sum of its proper divisors. In computer science, 221 is represented as 11011101 in binary and DD in hexadecimal. Historically, it is written as CCXXI in Roman numerals.
Factor Analysis
4 FactorsProperties
The prime factorization (13 × 17) reveals 2 prime building blocks.
Divisible by 2
221 ends in 1, so it is odd.
Divisible by 3
The digit sum 5 is not a multiple of 3.
Divisible by 4
The last two digits 21 are not divisible by 4.
Divisible by 5
221 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 5 is not a multiple of 9.
Divisible by 10
221 does not end in 0.
Divisible by 11
The alternating digit sum 1 is not a multiple of 11.
Deficient classification and digit analytics place 221 within several notable number theory sequences:
Timeline
Deep dive
How 221 breaks down
221 carries 4 distinct factors and a digit signature of 5 (5 as the digital root). The deficient classification indicates that its proper divisors sum to 31, which stays below the number, offering a quick glimpse into its abundance profile.
Numeral conversions provide additional context: the binary form 11011101 supports bitwise reasoning, hexadecimal DD aligns with computing notation, and the Roman numeral CCXXI keeps the encyclopedic tradition alive. These attributes make 221 useful for math olympiad problems, puzzle design, and code challenges alike.
Context
Where 221 shows up
Engineers lean on the divisibility profile when sizing circuits, mod designers use neighboring values (216–226) to tune search ranges, and educators feature 221 in worksheets about factor trees. Its binary footprint of length 8 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 221 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 221
Is 221 a prime number?
221 is composite with 4 total factors and the prime factorization 13 × 17.
What is the prime factorization of 221?
It breaks down as 13 × 17, multiplying the primes 13 × 17.
How is 221 represented in binary and hexadecimal?
221 converts to 11011101 in binary and DD in hexadecimal, which are helpful for computer science applications.
Is 221 a perfect square, cube, or triangular number?
221 is not a perfect square, is not a perfect cube, and is not triangular.
What are the digit sum and digital root of 221?
The digits sum to 5, producing a digital root of 5. These tests power divisibility shortcuts for 3 and 9.