Question: what are the evil numbers?
Answer: Evil Number. sum to 666 is known as an evil number (Pegg and Lomont 2004). However, the term "evil" is also used to denote nonnegative integers that have an even number of 1s in their binary expansions, the first few of which are 0, 3, 5, 6, 9, 10, 12, 15, 17, 18, 20, ...