30 has an infinite number of multiples. Some multiples of thirty include 30, 60, 90, 120 and 150. Three and 10 divide evenly into all multiples of 30.
The prime factors of 30 are two, three and five. All multiples of 30 are also multiples of both three and 10 because all multiples of any number must be multiples of all prime factors of that number. Thus, any number divisible by both three and 10 is a multiple of 30.
Divisibility rules state that all multiples of 10 end in zero, and all multiples of three have digits that add up to a number divisible by three. Thus, all multiples of 30 end in zero and their digits add up to a number divisible by three.