665621016656 has 10 divisors (see below), whose sum is σ = 1289640719802. Its totient is φ = 332810508320.

The previous prime is 665621016649. The next prime is 665621016719. The reversal of 665621016656 is 656610126566.

It can be written as a sum of positive squares in only one way, i.e., 522752136256 + 142868880400 = 723016^2 + 377980^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20800656755 + ... + 20800656786.

Almost surely, 2^665621016656 is an apocalyptic number.

It is an amenable number.

665621016656 is a deficient number, since it is larger than the sum of its proper divisors (624019703146).

665621016656 is a wasteful number, since it uses less digits than its factorization.

665621016656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41601313549 (or 41601313543 counting only the distinct ones).

The product of its (nonzero) digits is 2332800, while the sum is 50.

The spelling of 665621016656 in words is "six hundred sixty-five billion, six hundred twenty-one million, sixteen thousand, six hundred fifty-six".