6191

6191 is a natural number, the integer that follows 6190 and precedes 6192. In mathematics, it is notable for being a semiprime: a product of two distinct primes, namely 41 and 151. Its divisors are 1, 41, 151, and 6191, giving it exactly four divisors and a prime factorization of 6191 = 41 × 151.

As an odd composite, 6191 has several standard representations. It can be expressed as the difference of two squares: 6191 = 96^2 − 55^2. In binary, it is 1100000101111_2, and in hexadecimal it is 0x182F. The number cannot be written as a sum of two integer squares, since its prime factorization contains a prime congruent to 3 modulo 4 (151) to an odd power.

Euler's totient function yields φ(6191) = (41−1)(151−1) = 40 × 150 = 6000. This reflects the count of integers up to 6191 that are relatively prime to it.

As a semiprime, 6191 has relevance in introductory discussions of prime factorization and cryptographic concepts, where semiprimes are used to illustrate the difficulty of factoring. Its simple factorization also makes it a convenient example in classroom exercises.