664646135321021 has 16 divisors (see below), whose sum is σ = 786470051155200. Its totient is φ = 549574912309248.

The previous prime is 664646135320997. The next prime is 664646135321029. The reversal of 664646135321021 is 120123531646466.

It is a happy number.

It is a de Polignac number, because none of the positive numbers 2^k-664646135321021 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664646135321029) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1419592001 + ... + 1420060118.

It is an arithmetic number, because the mean of its divisors is an integer number (49154378197200).

Almost surely, 2^{664646135321021} is an apocalyptic number.

It is an amenable number.

664646135321021 is a deficient number, since it is larger than the sum of its proper divisors (121823915834179).

664646135321021 is a wasteful number, since it uses less digits than its factorization.

664646135321021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2839653308.

The product of its (nonzero) digits is 3732480, while the sum is 50.

Adding to 664646135321021 its reverse (120123531646466), we get a palindrome (784769666967487).

The spelling of 664646135321021 in words is "six hundred sixty-four trillion, six hundred forty-six billion, one hundred thirty-five million, three hundred twenty-one thousand, twenty-one".