66815685 has 60 divisors (see below), whose sum is σ = 126685548. Its totient is φ = 33685632.

The previous prime is 66815663. The next prime is 66815687. The reversal of 66815685 is 58651866.

66815685 is a `hidden beast` number, since 6 + 6 + 81 + 568 + 5 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 42224004 + 24591681 = 6498^2 + 4959^2 .

It is not a de Polignac number, because 66815685 - 2¹⁰ = 66814661 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

Its product of digits (345600) is a multiple of the sum of its prime factors (512).

It is a self number, because there is not a number n which added to its sum of digits gives 66815685.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66815687) by changing a digit.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 145977 + ... + 146433.

Almost surely, 2^66815685 is an apocalyptic number.

It is an amenable number.

66815685 is a deficient number, since it is larger than the sum of its proper divisors (59869863).

66815685 is a wasteful number, since it uses less digits than its factorization.

66815685 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 512 (or 484 counting only the distinct ones).

The product of its digits is 345600, while the sum is 45.

The square root of 66815685 is about 8174.0861874585. The cubic root of 66815685 is about 405.7820280785.

The spelling of 66815685 in words is "sixty-six million, eight hundred fifteen thousand, six hundred eighty-five".