666818785 has 8 divisors (see below), whose sum is σ = 800485416. Its totient is φ = 533253120.

The previous prime is 666818777. The next prime is 666818791. The reversal of 666818785 is 587818666.

It can be written as a sum of positive squares in 4 ways, for example, as 50637456 + 616181329 = 7116^2 + 24823^2 .

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

It is not a de Polignac number, because 666818785 - 2³ = 666818777 is a prime.

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, 9856 + ... + 37825.

It is an arithmetic number, because the mean of its divisors is an integer number (100060677).

Almost surely, 2^666818785 is an apocalyptic number.

It is an amenable number.

666818785 is a deficient number, since it is larger than the sum of its proper divisors (133666631).

666818785 is a wasteful number, since it uses less digits than its factorization.

666818785 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50483.

The product of its digits is 3870720, while the sum is 55.

The square root of 666818785 is about 25822.8345655546. The cubic root of 666818785 is about 873.6469034854.

It can be divided in two parts, 66681 and 8785, that added together give a triangular number (75466 = T₃₈₈).

The spelling of 666818785 in words is "six hundred sixty-six million, eight hundred eighteen thousand, seven hundred eighty-five".