640665123 has 16 divisors (see below), whose sum is σ = 1027633920. Its totient is φ = 346826016.

The previous prime is 640665121. The next prime is 640665133. The reversal of 640665123 is 321566046.

640665123 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 640665123 - 2¹ = 640665121 is a prime.

It is not an unprimeable number, because it can be changed into a prime (640665121) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 802440 + ... + 803237.

It is an arithmetic number, because the mean of its divisors is an integer number (64227120).

Almost surely, 2^640665123 is an apocalyptic number.

640665123 is a deficient number, since it is larger than the sum of its proper divisors (386968797).

640665123 is a wasteful number, since it uses less digits than its factorization.

640665123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1605706.

The product of its (nonzero) digits is 25920, while the sum is 33.

The square root of 640665123 is about 25311.3635152277. The cubic root of 640665123 is about 862.0723068348.

The spelling of 640665123 in words is "six hundred forty million, six hundred sixty-five thousand, one hundred twenty-three".