640606205 has 4 divisors (see below), whose sum is σ = 768727452. Its totient is φ = 512484960.

The previous prime is 640606163. The next prime is 640606237. The reversal of 640606205 is 502606046.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 502606046 = 2 ⋅251303023.

It can be written as a sum of positive squares in 2 ways, for example, as 372760249 + 267845956 = 19307^2 + 16366^2 .

It is not a de Polignac number, because 640606205 - 2¹⁰ = 640605181 is a prime.

It is a Duffinian number.

It is a Curzon 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, 64060616 + ... + 64060625.

It is an arithmetic number, because the mean of its divisors is an integer number (192181863).

Almost surely, 2^640606205 is an apocalyptic number.

It is an amenable number.

640606205 is a deficient number, since it is larger than the sum of its proper divisors (128121247).

640606205 is a wasteful number, since it uses less digits than its factorization.

640606205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128121246.

The product of its (nonzero) digits is 8640, while the sum is 29.

The square root of 640606205 is about 25310.1996238671. The cubic root of 640606205 is about 862.0458795426.

The spelling of 640606205 in words is "six hundred forty million, six hundred six thousand, two hundred five".