664605021 has 16 divisors (see below), whose sum is σ = 944253504. Its totient is φ = 414345984.

The previous prime is 664605013. The next prime is 664605041. The reversal of 664605021 is 120506466.

It is not a de Polignac number, because 664605021 - 2³ = 664605013 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 664605021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664605041) 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, 33495 + ... + 49508.

It is an arithmetic number, because the mean of its divisors is an integer number (59015844).

Almost surely, 2^664605021 is an apocalyptic number.

It is an amenable number.

664605021 is a deficient number, since it is larger than the sum of its proper divisors (279648483).

664605021 is a wasteful number, since it uses less digits than its factorization.

664605021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83180.

The product of its (nonzero) digits is 8640, while the sum is 30.

The square root of 664605021 is about 25779.9344646180. The cubic root of 664605021 is about 872.6790281856.

The spelling of 664605021 in words is "six hundred sixty-four million, six hundred five thousand, twenty-one".