I divisori di 991991 sono 16, elencati qui di seguito: 1; 7; 11; 13; 77; 91; 143; 991; 1001; 6937; 10901; 12883; 76307; 90181; 141713; 991991
991972, 991973, 991974, 991975, 991976, 991977, 991978, 991979, 991980, 991981, 991982, 991983, 991984, 991985, 991986, 991987, 991988, 991989, 991990, 991992, 991993, 991994, 991995, 991996, 991997, 991998, 991999, 992000, 992001, 992002, 992003, 992004, 992005, 992006, 992007, 992008, 992009, 992010