septillion vs tredecillion

septillion

num

  • A billion quintillion: 1 followed by 42 zeros, 10⁴². 

  • A trillion trillion: 1 followed by 24 zeros, 10²⁴. 

tredecillion

num

  • 10⁴². 

How often have the words septillion and tredecillion occurred in a corpus of books? (source: Google Ngram Viewer )