491891 has 4 divisors (see below), whose sum is σ = 517800. Its totient is φ = 465984.

The previous prime is 491873. The next prime is 491899. The reversal of 491891 is 198194.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-491891 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (491899) 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, 12926 + ... + 12963.

It is an arithmetic number, because the mean of its divisors is an integer number (129450).

2⁴⁹¹⁸⁹¹ is an apocalyptic number.

491891 is a deficient number, since it is larger than the sum of its proper divisors (25909).

491891 is a wasteful number, since it uses less digits than its factorization.

491891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25908.

The product of its digits is 2592, while the sum is 32.

The square root of 491891 is about 701.3494136306. The cubic root of 491891 is about 78.9386373892.

The spelling of 491891 in words is "four hundred ninety-one thousand, eight hundred ninety-one".