664721593 has 4 divisors (see below), whose sum is σ = 699706960. Its totient is φ = 629736228.

The previous prime is 664721591. The next prime is 664721599. The reversal of 664721593 is 395127466.

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 not a de Polignac number, because 664721593 - 2¹ = 664721591 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (664721591) 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, 17492655 + ... + 17492692.

It is an arithmetic number, because the mean of its divisors is an integer number (174926740).

Almost surely, 2^664721593 is an apocalyptic number.

It is an amenable number.

664721593 is a deficient number, since it is larger than the sum of its proper divisors (34985367).

664721593 is a wasteful number, since it uses less digits than its factorization.

664721593 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34985366.

The product of its digits is 272160, while the sum is 43.

The square root of 664721593 is about 25782.1952711556. The cubic root of 664721593 is about 872.7300479588.

The spelling of 664721593 in words is "six hundred sixty-four million, seven hundred twenty-one thousand, five hundred ninety-three".