158991 has 16 divisors (see below), whose sum is σ = 248064. Its totient is φ = 88704.

The previous prime is 158981. The next prime is 158993. The reversal of 158991 is 199851.

It is not a de Polignac number, because 158991 - 2⁵ = 158959 is a prime.

158991 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (158993) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1351 + ... + 1463.

It is an arithmetic number, because the mean of its divisors is an integer number (15504).

2¹⁵⁸⁹⁹¹ is an apocalyptic number.

158991 is a deficient number, since it is larger than the sum of its proper divisors (89073).

158991 is a wasteful number, since it uses less digits than its factorization.

158991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 190.

The product of its digits is 3240, while the sum is 33.

The square root of 158991 is about 398.7367552659. The cubic root of 158991 is about 54.1739929604.

The spelling of 158991 in words is "one hundred fifty-eight thousand, nine hundred ninety-one".