666984739681 has 4 divisors (see below), whose sum is σ = 718291258132. Its totient is φ = 615678221232.

The previous prime is 666984739651. The next prime is 666984739703. The reversal of 666984739681 is 186937489666.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 358093331281 + 308891408400 = 598409^2 + 555780^2 .

It is a cyclic number.

It is not a de Polignac number, because 666984739681 - 2¹³ = 666984731489 is a prime.

It is a super-2 number, since 2×666984739681² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666984739651) 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, 25653259206 + ... + 25653259231.

It is an arithmetic number, because the mean of its divisors is an integer number (179572814533).

Almost surely, 2^666984739681 is an apocalyptic number.

It is an amenable number.

666984739681 is a deficient number, since it is larger than the sum of its proper divisors (51306518451).

666984739681 is a wasteful number, since it uses less digits than its factorization.

666984739681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51306518450.

The product of its digits is 564350976, while the sum is 73.

The spelling of 666984739681 in words is "six hundred sixty-six billion, nine hundred eighty-four million, seven hundred thirty-nine thousand, six hundred eighty-one".