65664021 has 4 divisors (see below), whose sum is σ = 87552032. Its totient is φ = 43776012.

The previous prime is 65663993. The next prime is 65664037. The reversal of 65664021 is 12046656.

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 65664021 - 2⁵ = 65663989 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 65664021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (65664041) 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, 10944001 + ... + 10944006.

It is an arithmetic number, because the mean of its divisors is an integer number (21888008).

Almost surely, 2^65664021 is an apocalyptic number.

It is an amenable number.

65664021 is a deficient number, since it is larger than the sum of its proper divisors (21888011).

65664021 is a wasteful number, since it uses less digits than its factorization.

65664021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21888010.

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

The square root of 65664021 is about 8103.3339435074. Note that the first 3 decimals coincide. The cubic root of 65664021 is about 403.4370918236.

The spelling of 65664021 in words is "sixty-five million, six hundred sixty-four thousand, twenty-one".