28
28 is a even composite number that follows 27 and precedes 29. It is composed of 6 distinct factors: 1, 2, 4, 7, 14, 28. Its prime factorization can be written as 2^2 × 7. 28 is classified as a perfect number based on the sum of its proper divisors. In computer science, 28 is represented as 11100 in binary and 1C in hexadecimal. Historically, it is written as XXVIII in Roman numerals. It also belongs to the triangular number sequence.
Factor Analysis
6 FactorsProperties
The prime factorization (2^2 × 7) reveals 3 prime building blocks.
Divisible by 2
28 ends in 8, so it is even.
Divisible by 3
The digit sum 10 is not a multiple of 3.
Divisible by 4
The last two digits 28 form a multiple of 4.
Divisible by 5
28 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
28 does not end in 0.
Divisible by 11
The alternating digit sum -6 is not a multiple of 11.
Perfect classification and digit analytics place 28 within several notable number theory sequences:
Timeline
Deep dive
How 28 breaks down
28 carries 6 distinct factors and a digit signature of 10 (1 as the digital root). The perfect classification indicates that its proper divisors sum to the number itself, offering a quick glimpse into its abundance profile.
Numeral conversions provide additional context: the binary form 11100 supports bitwise reasoning, hexadecimal 1C aligns with computing notation, and the Roman numeral XXVIII keeps the encyclopedic tradition alive. These attributes make 28 useful for math olympiad problems, puzzle design, and code challenges alike.
Context
Where 28 shows up
Engineers lean on the divisibility profile when sizing circuits, mod designers use neighboring values (23–33) to tune search ranges, and educators feature 28 in worksheets about factor trees. Its binary footprint of length 5 bits also makes it a solid example for teaching storage limits and overflow.
Beyond STEM, the classification and sequence tags (Composite numbers, Perfect numbers, Triangular numbers) help historians, numerologists, and trivia writers tie 28 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 28
Is 28 a prime number?
28 is composite with 6 total factors and the prime factorization 2^2 × 7.
What is the prime factorization of 28?
It breaks down as 2^2 × 7, multiplying the primes 2 × 2 × 7.
How is 28 represented in binary and hexadecimal?
28 converts to 11100 in binary and 1C in hexadecimal, which are helpful for computer science applications.
Is 28 a perfect square, cube, or triangular number?
28 is not a perfect square, is not a perfect cube, and is triangular.
What are the digit sum and digital root of 28?
The digits sum to 10, producing a digital root of 1. These tests power divisibility shortcuts for 3 and 9.