I divisori di 19911987 sono 20, elencati qui di seguito: 1; 3; 9; 27; 81; 293; 839; 879; 2517; 2637; 7551; 7911; 22653; 23733; 67959; 245827; 737481; 2212443; 6637329; 19911987
19911968, 19911969, 19911970, 19911971, 19911972, 19911973, 19911974, 19911975, 19911976, 19911977, 19911978, 19911979, 19911980, 19911981, 19911982, 19911983, 19911984, 19911985, 19911986, 19911988, 19911989, 19911990, 19911991, 19911992, 19911993, 19911994, 19911995, 19911996, 19911997, 19911998, 19911999, 19912000, 19912001, 19912002, 19912003, 19912004, 19912005, 19912006