28 (number)
From Halbeeg, the open encyclopedia · Af-Soomaali
100 languages
28 is a natural number that lies between 27 and 29. It consists of two digits: 2 and 8. In base ten, it is an even number, since 28 is divisible by 2 with no remainder.
The divisors of 28 are 1, 2, 4, 7, 14, and 28. When the proper divisors—1, 2, 4, 7, and 14—are summed, they total 28. For this reason, 28 is called a perfect number.
Mathematical properties
28 is the result of summing 1 + 2 + 3 + 4 + 5 + 6 + 7, making it a triangular number. It is also a composite number equal to 2 × 2 × 7, with smallest prime factors of 2 and 7. It is not prime, as it has divisors other than 1 and itself.
Everyday use
28 is the number of days in February in a common year without a leap day; in a leap year it becomes 29. Additionally, four weeks of seven days each sum to 28 days.
In other numbering systems, 28 can be written as 11100 in binary and 1C in hexadecimal. In Somali, the number is pronounced "siddeed iyo labaatan".