664434654517621 has 8 divisors (see below), whose sum is σ = 757635895649304. Its totient is φ = 577246396684800.

The previous prime is 664434654517603. The next prime is 664434654517639. The reversal of 664434654517621 is 126715456434466.

It is an interprime number because it is at equal distance from previous prime (664434654517603) and next prime (664434654517639).

It can be written as a sum of positive squares in 4 ways, for example, as 151005733056721 + 513428921460900 = 12288439^2 + 22658970^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 664434654517621 - 2²⁵ = 664434620963189 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 (664434654512621) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1503245824480 + ... + 1503245824921.

It is an arithmetic number, because the mean of its divisors is an integer number (94704486956163).

Almost surely, 2^{664434654517621} is an apocalyptic number.

It is an amenable number.

664434654517621 is a deficient number, since it is larger than the sum of its proper divisors (93201241131683).

664434654517621 is a wasteful number, since it uses less digits than its factorization.

664434654517621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3006491649431.

The product of its digits is 348364800, while the sum is 64.

The spelling of 664434654517621 in words is "six hundred sixty-four trillion, four hundred thirty-four billion, six hundred fifty-four million, five hundred seventeen thousand, six hundred twenty-one".