2158991 has 4 divisors (see below), whose sum is σ = 2186400. Its totient is φ = 2131584.

The previous prime is 2158979. The next prime is 2158993. The reversal of 2158991 is 1998512.

2158991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 2158991 - 2¹⁸ = 1896847 is a prime.

It is a super-2 number, since 2×2158991² = 9322484276162, which contains 22 as substring.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2158993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13586 + ... + 13743.

It is an arithmetic number, because the mean of its divisors is an integer number (546600).

2^2158991 is an apocalyptic number.

2158991 is a deficient number, since it is larger than the sum of its proper divisors (27409).

2158991 is an equidigital number, since it uses as much as digits as its factorization.

2158991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27408.

The product of its digits is 6480, while the sum is 35.

The square root of 2158991 is about 1469.3505368019. The cubic root of 2158991 is about 129.2459502614.

The spelling of 2158991 in words is "two million, one hundred fifty-eight thousand, nine hundred ninety-one".