666712779605 has 18 divisors (see below), whose sum is σ = 844423667766. Its totient is φ = 505271815056.

The previous prime is 666712779539. The next prime is 666712779619. The reversal of 666712779605 is 506977217666.

It can be written as a sum of positive squares in only one way, i.e., 533370223684 + 133342555921 = 730322^2 + 365161^2 .

It is not a de Polignac number, because 666712779605 - 2²⁴ = 666696002389 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 34680686 + ... + 34699904.

It is an arithmetic number, because the mean of its divisors is an integer number (46912425987).

Almost surely, 2^666712779605 is an apocalyptic number.

It is an amenable number.

666712779605 is a deficient number, since it is larger than the sum of its proper divisors (177710888161).

666712779605 is an frugal number, since it uses more digits than its factorization.

666712779605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38481 (or 19243 counting only the distinct ones).

The product of its (nonzero) digits is 40007520, while the sum is 62.

The spelling of 666712779605 in words is "six hundred sixty-six billion, seven hundred twelve million, seven hundred seventy-nine thousand, six hundred five".