157 (number)
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157 is a natural number that follows 156 and precedes 158. It is written in Hindi-Arabic numerals as "157" and in Roman numerals as "CLVII". It is a prime number, meaning that only 1 and itself divide it evenly.
Like other small numbers, 157 appears in elementary mathematics, coding, and everyday use of numbers (for example, road numbers, years, or quantities of things). The mathematical properties listed below are among the most commonly noted.
Mathematical properties
157 is the 37th prime number starting from 2. It is an odd number whose only divisors are 1 and 157. The sum of its digits (1+5+7) is 13, which is itself prime; therefore 157 is not divisible by 3.
When 157 is divided by 4, the remainder is 1. As is typical for primes of this form, 157 can be expressed as the sum of two squares: 157 = 11² + 6² (121 + 36). This representation is unique when considering unordered pairs.
Palindromic numbers
When the digits of 157 are reversed (read backwards), the result is 751, which is also a prime number. A prime number whose reversal is also prime and does not read the same forwards and backwards is called an "emirp" — 157 is one such number.
Relationship to adjacent numbers
The preceding number, 156, is an even number with prime factorization 2² × 3 × 13. The following number, 158, is 2 × 79. Therefore 157 does not form a direct twin prime pair, since 155 (5 × 31) and 159 (3 × 53) are both composite.