666542665 has 4 divisors (see below), whose sum is σ = 799851204. Its totient is φ = 533234128.

The previous prime is 666542663. The next prime is 666542683. The reversal of 666542665 is 566245666.

666542665 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 497334601 + 169208064 = 22301^2 + 13008^2 .

It is a cyclic number.

It is not a de Polignac number, because 666542665 - 2¹ = 666542663 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666542663) 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, 66654262 + ... + 66654271.

It is an arithmetic number, because the mean of its divisors is an integer number (199962801).

Almost surely, 2^666542665 is an apocalyptic number.

It is an amenable number.

666542665 is a deficient number, since it is larger than the sum of its proper divisors (133308539).

666542665 is a wasteful number, since it uses less digits than its factorization.

666542665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133308538.

The product of its digits is 1555200, while the sum is 46.

The square root of 666542665 is about 25817.4875810951. The cubic root of 666542665 is about 873.5262986610.

The spelling of 666542665 in words is "six hundred sixty-six million, five hundred forty-two thousand, six hundred sixty-five".