This semester, students have enriched their understanding of numbers: from single digits to double digits and even more digits, they know odd and even numbers, odd and even numbers, prime and composite numbers, multiples and factors, etc., according to What you have learned above, please classify the 20 numbers from 1 to 20 according to your favorite method.
本学期，同学们又丰富了对数的认识：从一位数到两位数以至于更多位数，知道了奇数和偶数，单数和双数，质数和合数，倍数和因数等等，根据以上所学，请你按照你喜欢的方式，把1-20这20个数进行分类．
<result>1</result>