665763207921 has 12 divisors (see below), whose sum is σ = 1099037676672. Its totient is φ = 380436118776.

The previous prime is 665763207919. The next prime is 665763207947. The reversal of 665763207921 is 129702367566.

665763207921 is a `hidden beast` number, since 66 + 576 + 3 + 2 + 0 + 7 + 9 + 2 + 1 = 666.

It is not a de Polignac number, because 665763207921 - 2¹ = 665763207919 is a prime.

It is not an unprimeable number, because it can be changed into a prime (665763202921) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5283834921 + ... + 5283835046.

It is an arithmetic number, because the mean of its divisors is an integer number (91586473056).

Almost surely, 2^665763207921 is an apocalyptic number.

It is an amenable number.

665763207921 is a deficient number, since it is larger than the sum of its proper divisors (433274468751).

665763207921 is a wasteful number, since it uses less digits than its factorization.

665763207921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10567669980 (or 10567669977 counting only the distinct ones).

The product of its (nonzero) digits is 5715360, while the sum is 54.

The spelling of 665763207921 in words is "six hundred sixty-five billion, seven hundred sixty-three million, two hundred seven thousand, nine hundred twenty-one".