491591 has 2 divisors, whose sum is σ = 491592. Its totient is φ = 491590.

The previous prime is 491581. The next prime is 491593. The reversal of 491591 is 195194.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 491591 - 2⁶ = 491527 is a prime.

It is a super-2 number, since 2×491591² = 483323422562, which contains 22 as substring.

Together with 491593, it forms a pair of twin primes.

It is a Chen prime.

It is equal to p₄₀₈₈₉ and since 491591 and 40889 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 491591.

It is not a weakly prime, because it can be changed into another prime (491593) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 245795 + 245796.

It is an arithmetic number, because the mean of its divisors is an integer number (245796).

2⁴⁹¹⁵⁹¹ is an apocalyptic number.

491591 is a deficient number, since it is larger than the sum of its proper divisors (1).

491591 is an equidigital number, since it uses as much as digits as its factorization.

491591 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1620, while the sum is 29.

The square root of 491591 is about 701.1355075875. The cubic root of 491591 is about 78.9225861318.

The spelling of 491591 in words is "four hundred ninety-one thousand, five hundred ninety-one".