181 (number)

← 180 181 182 →
← 180 181 182 183 184 185 186 187 188 189 → ← 0 100 200 300 400 500 600 700 800 900 →
Cardinal	one hundred and eighty-one
Ordinal	181st (one hundred and eighty-first)
Factorization	181
Divisors	1, 181
Roman numeral	CLXXXI
Binary	101101012
Ternary	202013
Quaternary	23114
Quinary	12115
Senary	5016
Octal	2658
Duodecimal	13112
Hexadecimal	B516
Vigesimal	9120
Base 36	5136

181 is a number. It comes after 180 and before 182.

In mathematics

• 181 is an odd number.
• It is a prime number, which means it can only be divided evenly by 1 and itself. It's the 42nd prime.
• 181 is a palindromic number, because it reads the same forward and backward.
• It is also a twin prime with 179 (two prime numbers that differ by 2).

• As a centered polygonal number, 181 is:

• a centered square number,
• a centered pentagonal number,
• a centered 18-gonal number, and
• a centered 30-gonal number.

In science

• 181 is the atomic mass of the most common isotope of tantalum (Ta).

Fun fact

• 181 is a prime number that is also palindromic. This makes it part of a special group of numbers known as palindromic primes.