640206664 has 16 divisors (see below), whose sum is σ = 1201000320. Its totient is φ = 319939920.

The previous prime is 640206659. The next prime is 640206673. The reversal of 640206664 is 466602046.

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, 2892 + ... + 35899.

It is an arithmetic number, because the mean of its divisors is an integer number (75062520).

Almost surely, 2^640206664 is an apocalyptic number.

It is an amenable number.

640206664 is a deficient number, since it is larger than the sum of its proper divisors (560793656).

640206664 is a wasteful number, since it uses less digits than its factorization.

640206664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40860 (or 40856 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 34.

The square root of 640206664 is about 25302.3055076015. The cubic root of 640206664 is about 861.8666252158.

The spelling of 640206664 in words is "six hundred forty million, two hundred six thousand, six hundred sixty-four".