640676808 has 108 divisors (see below), whose sum is σ = 1843036065. Its totient is φ = 201030336.

The previous prime is 640676797. The next prime is 640676809. The reversal of 640676808 is 808676046.

It is a happy number.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

It can be written as a sum of positive squares in 2 ways, for example, as 611968644 + 28708164 = 24738^2 + 5358^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=17898.

It is not an unprimeable number, because it can be changed into a prime (640676809) 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 26 ways as a sum of consecutive naturals, for example, 4080666 + ... + 4080822.

Almost surely, 2^640676808 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640676808

640676808 is an abundant number, since it is smaller than the sum of its proper divisors (1202359257).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640676808 is a wasteful number, since it uses less digits than its factorization.

640676808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 364 (or 181 counting only the distinct ones).

The product of its (nonzero) digits is 387072, while the sum is 45.

The square root of 640676808 is about 25311.5943393537. The cubic root of 640676808 is about 862.0775478743.

The spelling of 640676808 in words is "six hundred forty million, six hundred seventy-six thousand, eight hundred eight".