171981 has 12 divisors (see below), whose sum is σ = 252252. Its totient is φ = 112896.

The previous prime is 171947. The next prime is 172001. The reversal of 171981 is 189171.

171981 is nontrivially palindromic in base 8.

It can be written as a sum of positive squares in 2 ways, for example, as 133956 + 38025 = 366^2 + 195^2 .

It is not a de Polignac number, because 171981 - 2⁶ = 171917 is a prime.

It is a super-2 number, since 2×171981² = 59154928722, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 171981.

It is not an unprimeable number, because it can be changed into a prime (171481) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 775 + ... + 971.

It is an arithmetic number, because the mean of its divisors is an integer number (21021).

2¹⁷¹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

171981 is a deficient number, since it is larger than the sum of its proper divisors (80271).

171981 is a wasteful number, since it uses less digits than its factorization.

171981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 300 (or 297 counting only the distinct ones).

The product of its digits is 504, while the sum is 27.

The square root of 171981 is about 414.7059198999. The cubic root of 171981 is about 55.6109298251.

The spelling of 171981 in words is "one hundred seventy-one thousand, nine hundred eighty-one".