166431321 has 16 divisors (see below), whose sum is σ = 281788800. Its totient is φ = 95103504.

The previous prime is 166431311. The next prime is 166431347. The reversal of 166431321 is 123134661.

166431321 is a `hidden beast` number, since 1 + 6 + 643 + 13 + 2 + 1 = 666.

It is not a de Polignac number, because 166431321 - 2¹⁷ = 166300249 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (166431301) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 440106 + ... + 440483.

It is an arithmetic number, because the mean of its divisors is an integer number (17611800).

Almost surely, 2^166431321 is an apocalyptic number.

It is an amenable number.

166431321 is a deficient number, since it is larger than the sum of its proper divisors (115357479).

166431321 is an equidigital number, since it uses as much as digits as its factorization.

166431321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 880605 (or 880599 counting only the distinct ones).

The product of its digits is 2592, while the sum is 27.

The square root of 166431321 is about 12900.8263688804. The cubic root of 166431321 is about 550.0620547063.

Adding to 166431321 its reverse (123134661), we get a palindrome (289565982).

The spelling of 166431321 in words is "one hundred sixty-six million, four hundred thirty-one thousand, three hundred twenty-one".