181 (number)

181 (One hundred and eighty-one) is a natural number following 180 and preceding 182.

Mathematics:

• 181 is a prime number.
• It is a twin prime with 179.
• It is a Sophie Germain prime, as 2*181 + 1 = 363, which is divisible by 3 and hence not prime.
• It is a safe prime, as (181-1)/2 = 90 which is not prime.
• It is a Pythagorean prime, since it can be expressed in the form 4n+1. Specifically, 181 = (9 * 4) + 1.
• It is a unique prime in base 10, meaning there is no other prime number with the same digit pattern.

Other:

• In some cultures, the number 181 might hold symbolic significance. This meaning can vary greatly.
• It can appear as a designation number for roads, buildings, or other numbered systems. However, without context, the specifics are unknown.