🌐EnglishEnglishBahasa IndonesiaDeutschEspañolFrançaisItalianoPortuguêsSvenskaTiếng ViệtРусский한국어中文日本語EntityQ3343131· pop 23· linked from 228 articlesquasiperfect numberhypothetical number whose sum of divisors is twice the number plus 1Connectionsprime numberEntityFermat numberEntityCategoriesArithmetic dynamicsDivisor functionInteger sequencesUnsolved problems in number theory