Highly totient number
A highly totient number k {\displaystyle k} is an integer that has more solutions to the equation ϕ ( x ) = k {\displaystyle \phi (x)=k} , where ϕ {\displaystyle \phi } is Euler's totient function, than any integer smaller than it. The first few highly totient numbers are 1, 2, 4, 8, 12, 24, 48, 72, 144, 240, 432, 480, 576, 720, 1152, 1440 (sequence A097942 in the OEIS), with 2, 3, 4, 5, 6, 10, 11, 17, 21, 31, 34, 37, 38, 49, 54, and 72 (sequence A131934 in the OEIS) totient solutions respectively.