151 (number)
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151 is a natural number that follows 150 and precedes 152. It is an odd number, as it cannot be divided evenly by two, and it is a prime number—meaning its only divisors are 1 and 151 itself.
In the decimal system, 151 is a palindrome: it reads the same whether you go from left to right or right to left. For this reason it is called a "palindromic prime". The sum of its digits is 1+5+1 = 7.
Mathematical properties
151 is the 36th prime number starting from 2. It also forms a pair with 149 known as "twin primes" (two prime numbers whose difference is 2). The next prime number after 151 is 157.
151 is classified as a centered decagonal number, derived from the formula 5n²+5n+1. When n = 5, the result is 151. The sequence begins 1, 11, 31, 61, 101, 151.
Representation in other systems
In binary, 151 is written as 10010111. In Roman numerals it is represented as CLI. In base seven and other systems, the notation differs but the value remains the same.
General use
Like other small numbers, 151 is used in road numbers, legal codes, year counts, and initial numbers in encoding systems. These uses are matters of social and administrative convention, not mathematical properties specific to the number.