1 is NOT Prime - Numberphile
Why the open web links it
Explains why the number 1 is not considered a prime number in mathematics.
Linked by 5 independent sites, 2 of them widely read in the 2026-10 crawl of the open web, including wikipedia.org, todayifoundout.com, onlinemathlearning.com, mrrenwick.ca, replicant.gr.
Cited in 1 Wikipedia article, including Fundamental theorem of arithmetic.