166404921 has 4 divisors (see below), whose sum is σ = 221873232. Its totient is φ = 110936612.

The previous prime is 166404913. The next prime is 166404923. The reversal of 166404921 is 129404661.

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 166404921 - 2³ = 166404913 is a prime.

It is not an unprimeable number, because it can be changed into a prime (166404923) 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, 27734151 + ... + 27734156.

It is an arithmetic number, because the mean of its divisors is an integer number (55468308).

Almost surely, 2^166404921 is an apocalyptic number.

It is an amenable number.

166404921 is a deficient number, since it is larger than the sum of its proper divisors (55468311).

166404921 is an equidigital number, since it uses as much as digits as its factorization.

166404921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55468310.

The product of its (nonzero) digits is 10368, while the sum is 33.

The square root of 166404921 is about 12899.8031380328. The cubic root of 166404921 is about 550.0329688226.

The spelling of 166404921 in words is "one hundred sixty-six million, four hundred four thousand, nine hundred twenty-one".