Why is 1 not considered as a prime number?

Added: 2026-06-10

[00:00:00]Most people think one should be a prime number.

[00:00:03]After all, it can only be divided by itself, right?

[00:00:08]But a prime number has a special rule.

[00:00:10]It must have exactly two distinct factors, one and itself. For example, seven has only one and seven.

[00:00:16]Now, look at one.

[00:00:18]It only has one factor, itself, not two.

[00:00:23]Just one. And if one were prime, mathematics would become messy. Every number could have infinitely [music] many prime factorizations by multiplying extra ones.

[00:00:32]>> So, that's why one isn't a prime number.

[00:00:34]>> [music] >> Prime numbers need exactly two factors, and one has only one. That's why mathematicians keep it outside the prime number group.

[00:00:40]If one tiny number can surprise you this much, imagine what other secrets math and science are hiding. Follow for more mind-blowing facts.