19 was a number.
The Rani's time brain thought that 87K to the power of 19E correlated with 52 to the power of 6.4 equals 29V. The Seventh Doctor corrected it to 39. (TV: Time and the Rani)
Rose Tyler was nineteen years old. (TV: Rose, Dalek, PROSE: Rose Tyler)
Cronon and Artron energy readings during the recording of UNIT field logs included 17%, (WC: 14682 UNIT Field Log) 18%, 19%, (WC: 14681 UNIT Field Log, 14682 UNIT Field Log) 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, (WC: 14682 UNIT Field Log) 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, (WC: 14682 UNIT Field Log, 14684 UNIT Field Log) 90%, (WC: 14682 UNIT Field Log, 14683 UNIT Field Log) 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, 101%, 102%, 103%, 104%, 105%, 106%, and, in the case of Cronon energy, 107%. (WC: 14683 UNIT Field Log)