166604721 has 4 divisors (see below), whose sum is σ = 222139632. Its totient is φ = 111069812.

The previous prime is 166604717. The next prime is 166604723. The reversal of 166604721 is 127406661.

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 166604721 - 2² = 166604717 is a prime.

It is not an unprimeable number, because it can be changed into a prime (166604723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27767451 + ... + 27767456.

It is an arithmetic number, because the mean of its divisors is an integer number (55534908).

Almost surely, 2^166604721 is an apocalyptic number.

It is an amenable number.

166604721 is a deficient number, since it is larger than the sum of its proper divisors (55534911).

166604721 is an equidigital number, since it uses as much as digits as its factorization.

166604721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55534910.

The product of its (nonzero) digits is 12096, while the sum is 33.

The square root of 166604721 is about 12907.5451190379. The cubic root of 166604721 is about 550.2530196722.

The spelling of 166604721 in words is "one hundred sixty-six million, six hundred four thousand, seven hundred twenty-one".