165981 has 8 divisors (see below), whose sum is σ = 225184. Its totient is φ = 108720.

The previous prime is 165961. The next prime is 165983. The reversal of 165981 is 189561.

It is a happy number.

165981 is nontrivially palindromic in base 6.

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

It is not a de Polignac number, because 165981 - 2⁹ = 165469 is a prime.

It is a super-2 number, since 2×165981² = 55099384722, which contains 22 as substring.

It is a Duffinian number.

It is a plaindrome in base 14.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165983) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 271 + ... + 636.

It is an arithmetic number, because the mean of its divisors is an integer number (28148).

2¹⁶⁵⁹⁸¹ is an apocalyptic number.

It is an amenable number.

165981 is a deficient number, since it is larger than the sum of its proper divisors (59203).

165981 is an equidigital number, since it uses as much as digits as its factorization.

165981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 971.

The product of its digits is 2160, while the sum is 30.

The square root of 165981 is about 407.4076582491. The cubic root of 165981 is about 54.9565497051.

The spelling of 165981 in words is "one hundred sixty-five thousand, nine hundred eighty-one".