640530655 has 4 divisors (see below), whose sum is σ = 768636792. Its totient is φ = 512424520.

The previous prime is 640530637. The next prime is 640530661. The reversal of 640530655 is 556035046.

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

It is not a de Polignac number, because 640530655 - 2¹¹ = 640528607 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 640530655.

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, 64053061 + ... + 64053070.

It is an arithmetic number, because the mean of its divisors is an integer number (192159198).

Almost surely, 2^640530655 is an apocalyptic number.

640530655 is a deficient number, since it is larger than the sum of its proper divisors (128106137).

640530655 is a wasteful number, since it uses less digits than its factorization.

640530655 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128106136.

The product of its (nonzero) digits is 54000, while the sum is 34.

The square root of 640530655 is about 25308.7070985461. The cubic root of 640530655 is about 862.0119897019.

The spelling of 640530655 in words is "six hundred forty million, five hundred thirty thousand, six hundred fifty-five".