640808404 has 24 divisors (see below), whose sum is σ = 1188167400. Its totient is φ = 301357056.

The previous prime is 640808401. The next prime is 640808411. The reversal of 640808404 is 404808046.

It can be written as a sum of positive squares in 4 ways, for example, as 176836804 + 463971600 = 13298^2 + 21540^2 .

It is a Harshad number since it is a multiple of its sum of digits (34).

It is a self number, because there is not a number n which added to its sum of digits gives 640808404.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640808401) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 171484 + ... + 175180.

It is an arithmetic number, because the mean of its divisors is an integer number (49506975).

Almost surely, 2^640808404 is an apocalyptic number.

It is an amenable number.

640808404 is a deficient number, since it is larger than the sum of its proper divisors (547358996).

640808404 is a wasteful number, since it uses less digits than its factorization.

640808404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6267 (or 6265 counting only the distinct ones).

The product of its (nonzero) digits is 24576, while the sum is 34.

The square root of 640808404 is about 25314.1937260502. The cubic root of 640808404 is about 862.1365678509.

The spelling of 640808404 in words is "six hundred forty million, eight hundred eight thousand, four hundred four".