666791817785 has 8 divisors (see below), whose sum is σ = 847217839176. Its totient is φ = 502055015680.

The previous prime is 666791817733. The next prime is 666791817793. The reversal of 666791817785 is 587718197666.

It can be written as a sum of positive squares in 4 ways, for example, as 109684828969 + 557106988816 = 331187^2 + 746396^2 .

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

It is not a de Polignac number, because 666791817785 - 2¹² = 666791813689 is a prime.

It is a super-2 number, since 2×666791817785² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3922304726 + ... + 3922304895.

It is an arithmetic number, because the mean of its divisors is an integer number (105902229897).

Almost surely, 2^666791817785 is an apocalyptic number.

It is an amenable number.

666791817785 is a deficient number, since it is larger than the sum of its proper divisors (180426021391).

666791817785 is a wasteful number, since it uses less digits than its factorization.

666791817785 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7844609643.

The product of its digits is 213373440, while the sum is 71.

The spelling of 666791817785 in words is "six hundred sixty-six billion, seven hundred ninety-one million, eight hundred seventeen thousand, seven hundred eighty-five".