509891 has 4 divisors (see below), whose sum is σ = 511632. Its totient is φ = 508152.

The previous prime is 509879. The next prime is 509909. The reversal of 509891 is 198905.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 509891 - 2¹⁰ = 508867 is a prime.

It is a Duffinian number.

It is a zygodrome in base 2.

It is not an unprimeable number, because it can be changed into a prime (509801) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 311 + ... + 1056.

It is an arithmetic number, because the mean of its divisors is an integer number (127908).

2⁵⁰⁹⁸⁹¹ is an apocalyptic number.

509891 is a deficient number, since it is larger than the sum of its proper divisors (1741).

509891 is a wasteful number, since it uses less digits than its factorization.

509891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1740.

The product of its (nonzero) digits is 3240, while the sum is 32.

The square root of 509891 is about 714.0665235116. The cubic root of 509891 is about 79.8900050833.

The spelling of 509891 in words is "five hundred nine thousand, eight hundred ninety-one".