6431

6431 is a natural number that follows 6430 and precedes 6432. In number theory, it is notable for being a semiprime: it factors into two prime numbers, 59 and 109. As the product of two primes, 6431 is odd and not a prime itself, yet it has exactly four positive divisors: 1, 59, 109, and 6431.

In decimal notation, 6431 is written as itself. Its representations in other bases include binary 1100100011111 and hexadecimal 0x191F. The digit sum in decimal is 14, and the number is congruent to 3 modulo 4 (since 6431 ≡ 3 mod 4). The factorization 59 × 109 reflects its semiprime status, with both factors being primes.

Historically and in education, semiprimes like 6431 are used to illustrate basic factorization concepts and primality testing on small examples. While 6431 itself is not used in cryptographic practice due to its small size, semiprimes as a class are central to certain cryptographic protocols that rely on the difficulty of factoring large semiprimes.

Roman numerals render 6431 as an informal MMMMMMCDXXXI, acknowledging that standard modern usage typically employs overline notation for large thousands. Overall, 6431 is a composite, semiprime example that highlights the multiplicative structure of integers and their base representations.

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