664465681 has 4 divisors (see below), whose sum is σ = 724871664. Its totient is φ = 604059700.

The previous prime is 664465657. The next prime is 664465691. The reversal of 664465681 is 186564466.

664465681 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 664465681 - 2¹⁹ = 663941393 is a prime.

It is a super-2 number, since 2×664465681² = 883029282453587522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (664465691) 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, 30202975 + ... + 30202996.

It is an arithmetic number, because the mean of its divisors is an integer number (181217916).

Almost surely, 2^664465681 is an apocalyptic number.

It is an amenable number.

664465681 is a deficient number, since it is larger than the sum of its proper divisors (60405983).

664465681 is a wasteful number, since it uses less digits than its factorization.

664465681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60405982.

The product of its digits is 829440, while the sum is 46.

The square root of 664465681 is about 25777.2318335387. The cubic root of 664465681 is about 872.6180357710.

It can be divided in two parts, 66446 and 5681, that added together give a palindrome (72127).

The spelling of 664465681 in words is "six hundred sixty-four million, four hundred sixty-five thousand, six hundred eighty-one".