721
721 is a odd composite number that follows 720 and precedes 722. It is composed of 4 distinct factors: 1, 7, 103, 721. Its prime factorization can be written as 7 × 103. 721 is classified as a deficient number based on the sum of its proper divisors. In computer science, 721 is represented as 1011010001 in binary and 2D1 in hexadecimal. Historically, it is written as DCCXXI in Roman numerals.
Factor Analysis
4 FactorsProperties
The prime factorization (7 × 103) reveals 2 prime building blocks.
Divisible by 2
721 ends in 1, so it is odd.
Divisible by 3
The digit sum 10 is not a multiple of 3.
Divisible by 4
The last two digits 21 are not divisible by 4.
Divisible by 5
721 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 10 is not a multiple of 9.
Divisible by 10
721 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 721 within several notable number theory sequences:
Timeline
Deep dive
How 721 breaks down
721 carries 4 distinct factors and a digit signature of 10 (1 as the digital root). The deficient classification indicates that its proper divisors sum to 111, which stays below the number, offering a quick glimpse into its abundance profile.
Numeral conversions provide additional context: the binary form 1011010001 supports bitwise reasoning, hexadecimal 2D1 aligns with computing notation, and the Roman numeral DCCXXI keeps the encyclopedic tradition alive. These attributes make 721 useful for math olympiad problems, puzzle design, and code challenges alike.
Context
Where 721 shows up
Engineers lean on the divisibility profile when sizing circuits, mod designers use neighboring values (716–726) to tune search ranges, and educators feature 721 in worksheets about factor trees. Its binary footprint of length 10 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 721 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 721
Is 721 a prime number?
721 is composite with 4 total factors and the prime factorization 7 × 103.
What is the prime factorization of 721?
It breaks down as 7 × 103, multiplying the primes 7 × 103.
How is 721 represented in binary and hexadecimal?
721 converts to 1011010001 in binary and 2D1 in hexadecimal, which are helpful for computer science applications.
Is 721 a perfect square, cube, or triangular number?
721 is not a perfect square, is not a perfect cube, and is not triangular.
What are the digit sum and digital root of 721?
The digits sum to 10, producing a digital root of 1. These tests power divisibility shortcuts for 3 and 9.