640590865 has 8 divisors (see below), whose sum is σ = 770888808. Its totient is φ = 511019520.

The previous prime is 640590857. The next prime is 640590877. The reversal of 640590865 is 568095046.

It can be written as a sum of positive squares in 4 ways, for example, as 3129361 + 637461504 = 1769^2 + 25248^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 640590865 - 2³ = 640590857 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 179706 + ... + 183235.

It is an arithmetic number, because the mean of its divisors is an integer number (96361101).

Almost surely, 2^640590865 is an apocalyptic number.

It is an amenable number.

640590865 is a deficient number, since it is larger than the sum of its proper divisors (130297943).

640590865 is a wasteful number, since it uses less digits than its factorization.

640590865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 363299.

The product of its (nonzero) digits is 259200, while the sum is 43.

The square root of 640590865 is about 25309.8965821672. The cubic root of 640590865 is about 862.0389986178.

The spelling of 640590865 in words is "six hundred forty million, five hundred ninety thousand, eight hundred sixty-five".