666640801 has 4 divisors (see below), whose sum is σ = 666881604. Its totient is φ = 666400000.

The previous prime is 666640769. The next prime is 666640813. The reversal of 666640801 is 108046666.

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 352500625 + 314140176 = 18775^2 + 17724^2 .

It is a cyclic number.

It is not a de Polignac number, because 666640801 - 2⁵ = 666640769 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666640841) 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, 116200 + ... + 121801.

It is an arithmetic number, because the mean of its divisors is an integer number (166720401).

Almost surely, 2^666640801 is an apocalyptic number.

It is an amenable number.

666640801 is a deficient number, since it is larger than the sum of its proper divisors (240803).

666640801 is a wasteful number, since it uses less digits than its factorization.

666640801 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 240802.

The product of its (nonzero) digits is 41472, while the sum is 37.

The square root of 666640801 is about 25819.3880833764. The cubic root of 666640801 is about 873.5691667196.

The spelling of 666640801 in words is "six hundred sixty-six million, six hundred forty thousand, eight hundred one".