166381 has 4 divisors (see below), whose sum is σ = 167200. Its totient is φ = 165564.

The previous prime is 166363. The next prime is 166393. The reversal of 166381 is 183661.

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 a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 166381 - 2⁵ = 166349 is a prime.

It is a super-2 number, since 2×166381² = 55365274322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166301) 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, 160 + ... + 598.

It is an arithmetic number, because the mean of its divisors is an integer number (41800).

166381 is a Friedman number, since it can be written as 6+(8*(6+1)-1)^3, using all its digits and the basic arithmetic operations.

2¹⁶⁶³⁸¹ is an apocalyptic number.

166381 is the 236-th hex number.

It is an amenable number.

166381 is a deficient number, since it is larger than the sum of its proper divisors (819).

166381 is an equidigital number, since it uses as much as digits as its factorization.

166381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 818.

The product of its digits is 864, while the sum is 25.

The square root of 166381 is about 407.8982716315. The cubic root of 166381 is about 55.0006611491. Note that the first 3 decimals are identical.

The spelling of 166381 in words is "one hundred sixty-six thousand, three hundred eighty-one".