Untouchable Number: Integer, Sum, Proper Divisor, Goldbach Conjecture, Composite Number, Perfect Number

Semiperfect Number: Mathematics, Number Theory, Natural Number, Proper Divisor, Perfect Prime

Perfect Totient Number: Number Theory, Integer,

Superperfect Number: Perfect Number, Mersenne Prme, Divisor Function, 2 (Number), 4 (Number)

Weird Number: Natural Number, Number Theory, Divisor