640644055 has 4 divisors (see below), whose sum is σ = 768772872. Its totient is φ = 512515240.

The previous prime is 640644029. The next prime is 640644091. The reversal of 640644055 is 550446046.

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

It is not a de Polignac number, because 640644055 - 2⁵ = 640644023 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 640644055.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64064401 + ... + 64064410.

It is an arithmetic number, because the mean of its divisors is an integer number (192193218).

Almost surely, 2^640644055 is an apocalyptic number.

640644055 is a deficient number, since it is larger than the sum of its proper divisors (128128817).

640644055 is a wasteful number, since it uses less digits than its factorization.

640644055 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128128816.

The product of its (nonzero) digits is 57600, while the sum is 34.

The square root of 640644055 is about 25310.9473350959. The cubic root of 640644055 is about 862.0628571042.

The spelling of 640644055 in words is "six hundred forty million, six hundred forty-four thousand, fifty-five".