805991 has 2 divisors, whose sum is σ = 805992. Its totient is φ = 805990.

The previous prime is 805967. The next prime is 806009. The reversal of 805991 is 199508.

805991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-805991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (805901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 402995 + 402996.

It is an arithmetic number, because the mean of its divisors is an integer number (402996).

2⁸⁰⁵⁹⁹¹ is an apocalyptic number.

805991 is a deficient number, since it is larger than the sum of its proper divisors (1).

805991 is an equidigital number, since it uses as much as digits as its factorization.

805991 is an evil number, because the sum of its binary digits is even.

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

The square root of 805991 is about 897.7700150930. The cubic root of 805991 is about 93.0629319301.

The spelling of 805991 in words is "eight hundred five thousand, nine hundred ninety-one".