159981 has 4 divisors (see below), whose sum is σ = 213312. Its totient is φ = 106652.

The previous prime is 159979. The next prime is 160001. The reversal of 159981 is 189951.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 189951 = 3 ⋅63317.

It is a cyclic number.

It is not a de Polignac number, because 159981 - 2¹ = 159979 is a prime.

It is a super-2 number, since 2×159981² = 51187840722, which contains 22 as substring.

It is an Ulam number.

It is a D-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 polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26661 + ... + 26666.

It is an arithmetic number, because the mean of its divisors is an integer number (53328).

2¹⁵⁹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

159981 is a deficient number, since it is larger than the sum of its proper divisors (53331).

159981 is an equidigital number, since it uses as much as digits as its factorization.

159981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53330.

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

The square root of 159981 is about 399.9762492949. The cubic root of 159981 is about 54.2862033329.

The spelling of 159981 in words is "one hundred fifty-nine thousand, nine hundred eighty-one".