EntityQ301128· pop 13· linked from 228 articlesRiesel numberSign in to saveodd natural number k such that k·2^n − 1 is composite for all natural nConnectionsprime numberEntityfigurate numberEntitySierpinski numberEntityautomorphic numberEntityPrimeGridEntitymathematicsEntityInternational Standard Book NumberEntitynatural numberEntityintegerEntitysetEntitybinary numeral systemEntitydigitEntityexponentiationEntitynumeral systemEntitygreatest common divisorEntitythree-dimensional spaceEntityparityEntitynatural languageEntitycomposite numberEntityperfect numberEntityCategoriesAnalytic number theoryPrime numbersUnsolved problems in number theory