Fatto generale: 78 is the number of chromosomes in canine DNA.
Fatto matematico: 78 is the smallest number that can be written as the sum of of 4 distinct squares in 3 ways.
Trivia: 78 is the number of lines that make up Metatron's Cube.
Data storica: March 18th is the day in 235 that Emperor Alexander Severus and his mother Julia Mamaea are murdered by legionaries near Moguntiacum (modern Mainz).