666540065 has 4 divisors (see below), whose sum is σ = 799848084. Its totient is φ = 533232048.

The previous prime is 666540019. The next prime is 666540067. The reversal of 666540065 is 560045666.

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 384434449 + 282105616 = 19607^2 + 16796^2 .

It is a cyclic number.

It is not a de Polignac number, because 666540065 - 2⁶ = 666540001 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666540067) 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, 66654002 + ... + 66654011.

It is an arithmetic number, because the mean of its divisors is an integer number (199962021).

Almost surely, 2^666540065 is an apocalyptic number.

It is an amenable number.

666540065 is a deficient number, since it is larger than the sum of its proper divisors (133308019).

666540065 is a wasteful number, since it uses less digits than its factorization.

666540065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133308018.

The product of its (nonzero) digits is 129600, while the sum is 38.

The square root of 666540065 is about 25817.4372275793. The cubic root of 666540065 is about 873.5251628641.

The spelling of 666540065 in words is "six hundred sixty-six million, five hundred forty thousand, sixty-five".