131 (number)

131 is a natural number that falls between 130 and 132 in sequence. In the decimal system it comprises three digits: 1, 3, and 1.

131 is a prime number, meaning it cannot be divided by any whole number other than 1 and itself. It is also a palindrome—it reads the same forwards and backwards—and is therefore classified as a palindromic prime.

Mathematical properties

All permutations of the digits of 131—namely 113, 131, and 311—are prime numbers. Because of this property, 131 belongs to the class of permutable primes, which are prime numbers that remain prime under any rearrangement of their digits.

131 is a Sophie Germain prime, since 2 × 131 + 1 = 263, which is also prime. It is also the sum of three consecutive prime numbers: 41 + 43 + 47 = 131.

131 does not have a twin prime, as both 129 and 133 are composite: 129 = 3 × 43 and 133 = 7 × 19.

Notation and other systems

In Roman numerals, 131 is written as CXXXI. In binary it is 10000011, and in hexadecimal it is 83.