159991 has 8 divisors (see below), whose sum is σ = 178304. Its totient is φ = 142560.

The previous prime is 159979. The next prime is 160001. The reversal of 159991 is 199951.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 159991 - 2¹³ = 151799 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (159911) 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 7 ways as a sum of consecutive naturals, for example, 205 + ... + 601.

It is an arithmetic number, because the mean of its divisors is an integer number (22288).

159991 is a Friedman number, since it can be written as (11+9)^(9-5)-9, using all its digits and the basic arithmetic operations.

2¹⁵⁹⁹⁹¹ is an apocalyptic number.

159991 is a deficient number, since it is larger than the sum of its proper divisors (18313).

159991 is a wasteful number, since it uses less digits than its factorization.

159991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 441.

The product of its digits is 3645, while the sum is 34.

The square root of 159991 is about 399.9887498418. The cubic root of 159991 is about 54.2873344062.

The spelling of 159991 in words is "one hundred fifty-nine thousand, nine hundred ninety-one".