640344805 has 4 divisors (see below), whose sum is σ = 768413772. Its totient is φ = 512275840.

The previous prime is 640344769. The next prime is 640344823. The reversal of 640344805 is 508443046.

640344805 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 508443046 = 2 ⋅254221523.

It can be written as a sum of positive squares in 2 ways, for example, as 337897924 + 302446881 = 18382^2 + 17391^2 .

It is not a de Polignac number, because 640344805 - 2²¹ = 638247653 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64034476 + ... + 64034485.

It is an arithmetic number, because the mean of its divisors is an integer number (192103443).

Almost surely, 2^640344805 is an apocalyptic number.

It is an amenable number.

640344805 is a deficient number, since it is larger than the sum of its proper divisors (128068967).

640344805 is a wasteful number, since it uses less digits than its factorization.

640344805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128068966.

The product of its (nonzero) digits is 46080, while the sum is 34.

The square root of 640344805 is about 25305.0351708904. The cubic root of 640344805 is about 861.9286106973.

The spelling of 640344805 in words is "six hundred forty million, three hundred forty-four thousand, eight hundred five".