666640799 has 4 divisors (see below), whose sum is σ = 727244520. Its totient is φ = 606037080.

The previous prime is 666640769. The next prime is 666640813. The reversal of 666640799 is 997046666.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 666640799 - 2¹⁶ = 666575263 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 666640799.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666640769) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 30301844 + ... + 30301865.

It is an arithmetic number, because the mean of its divisors is an integer number (181811130).

Almost surely, 2^666640799 is an apocalyptic number.

666640799 is a deficient number, since it is larger than the sum of its proper divisors (60603721).

666640799 is a wasteful number, since it uses less digits than its factorization.

666640799 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60603720.

The product of its (nonzero) digits is 2939328, while the sum is 53.

The square root of 666640799 is about 25819.3880446458. The cubic root of 666640799 is about 873.5691658460.

The spelling of 666640799 in words is "six hundred sixty-six million, six hundred forty thousand, seven hundred ninety-nine".