155981 has 4 divisors (see below), whose sum is σ = 178272. Its totient is φ = 133692.

The previous prime is 155921. The next prime is 156007. The reversal of 155981 is 189551.

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.

It is a cyclic number.

It is not a de Polignac number, because 155981 - 2¹⁴ = 139597 is a prime.

It is a super-2 number, since 2×155981² = 48660144722, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a nialpdrome in base 11.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (155921) 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, 11135 + ... + 11148.

It is an arithmetic number, because the mean of its divisors is an integer number (44568).

2¹⁵⁵⁹⁸¹ is an apocalyptic number.

It is an amenable number.

155981 is a deficient number, since it is larger than the sum of its proper divisors (22291).

155981 is an equidigital number, since it uses as much as digits as its factorization.

155981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22290.

The product of its digits is 1800, while the sum is 29.

The square root of 155981 is about 394.9442998702. The cubic root of 155981 is about 53.8299405398.

The spelling of 155981 in words is "one hundred fifty-five thousand, nine hundred eighty-one".