5509

5509 is a natural number that follows 5508 and precedes 5510. In mathematics, it is notable as an odd composite number and, more specifically, as a semiprime.

Its prime factorization is 5509 = 7 × 787, with 7 and 787 being distinct primes. Because its prime factors are distinct, 5509 is squarefree and has exactly four positive divisors: 1, 7, 787, and 5509. The number is not prime, and it is not a perfect power. Its Euler totient is φ(5509) = (7 − 1)(787 − 1) = 6 × 786 = 4716. The digital root of 5509 is 1 (5 + 5 + 0 + 9 = 19; 1 + 9 = 10; 1 + 0 = 1).

In base representations, 5509 is 1010110000101 in binary and 0x1585 in hexadecimal. It is odd and congruent to 1 modulo 4, while being divisible by 7 and 787 by definition.

As a semiprime, 5509 serves as a straightforward example in number theory discussions of factorization and divisor structure. Its simple two-prime factorization provides a clear illustration of how composite numbers can arise from the product of two primes.

See also: 5508, 5510.