858991 has 12 divisors (see below), whose sum is σ = 1020016. Its totient is φ = 708480.

The previous prime is 858989. The next prime is 858997. The reversal of 858991 is 199858.

It is not a de Polignac number, because 858991 - 2¹ = 858989 is a prime.

It is an Ulam number.

It is a Duffinian number.

Its product of digits (25920) is a multiple of the sum of its prime factors (162).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (858997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 11731 + ... + 11803.

2⁸⁵⁸⁹⁹¹ is an apocalyptic number.

858991 is a deficient number, since it is larger than the sum of its proper divisors (161025).

858991 is an equidigital number, since it uses as much as digits as its factorization.

858991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 162 (or 121 counting only the distinct ones).

The product of its digits is 25920, while the sum is 40.

The square root of 858991 is about 926.8176735475. The cubic root of 858991 is about 95.0596485973.

It can be divided in two parts, 858 and 991, that added together give a square (1849 = 43²).

The spelling of 858991 in words is "eight hundred fifty-eight thousand, nine hundred ninety-one".