List of champions for factoring Cunningham numbers: Quadratic sieve method: 3138 C116 10,142+ A. K. Lenstra & M. Manasse & al. with many computers 3306 C114 3,311- A. K. Lenstra & M. Manasse & al. with many computers Elliptic curve method: 3335 P42 10,201- D. Rusin with a SparcStation 2859 P38 11,118+ A. K. Lenstra & M. Manasse with several computers Largest penultimate prime factor (ultimate factor shown also): 3338 p58*p76 2,467- R. Silverman with several computers 2894 p56*p66 7,149+ A. K. Lenstra & M. Manasse with several computers 3195 p56*p58 10,151- A. K. Lenstra & M. Manasse & al. with many computers 3310 p56*p68 3,269+ R. Silverman with several computers First five holes in each table on June 24, 1992: 2,479- c127 2,511- c123 2,515- c114 2,523- c158 2,527- c145 2,481+ c122 2,485+ c116 2,491+ c123 2,503+ c151 2,509+ c150 2,802M c104 2,814L c109 2,830L c99 2,838L c116 2,842L c110 2,488+ c145 2,524+ c119 2,536+ c156 2,548+ c157 2,556+ c134 3,319- c119 3,331- c139 3,349- c167 3,359- c157 3,365- c111 3,277+ c128 3,278+ c107 3,283+ c114 3,293+ c122 3,295+ c111 5,187- c106 5,229- c129 5,233- c148 5,241- c117 5,247- c147 5,187+ c105 5,191+ c114 5,193+ c124 5,202+ c112 5,206+ c143 6,173- c119 6,179- c115 6,187- c107 6,199- c122 6,203- c122 6,169+ c101 6,172+ c99 6,176+ c125 6,178+ c137 6,184+ c100 7,169- c132 7,173- c146 7,187- c121 7,193- c136 7,199- c164 7,163+ c117 7,164+ c136 7,169+ c128 7,172+ c114 7,173+ c123 10,157- c132 10,163- c163 10,167- c142 10,169- c152 10,173- c154 10,149+ c123 10,158+ c153 10,163+ c139 10,166+ c164 10,167+ c118 11,131- c134 11,151- c139 11,167- c128 11,169- c151 11,177- c104 11,127+ c120 11,131+ c129 11,139+ c114 11,142+ c141 11,146+ c132 12,137- c123 12,139- c119 12,149- c156 12,151- c162 12,161- c135 12,127+ c99 12,131+ c136 12,136+ c104 12,146+ c140 12,148+ c156 Here is the current list of smaller but needed numbers: 2,802M c104 2,830L c99 2,854L c98 2,854M c102 2,862L c100 2,874M c102 5,187+ c105 6,169+ c101 6,172+ c99 12,127+ c99 12,136+ c104