640460666 has 4 divisors (see below), whose sum is σ = 960691002. Its totient is φ = 320230332.

The previous prime is 640460641. The next prime is 640460671. The reversal of 640460666 is 666064046.

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

It can be written as a sum of positive squares in only one way, i.e., 348905041 + 291555625 = 18679^2 + 17075^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160115165 + ... + 160115168.

Almost surely, 2^640460666 is an apocalyptic number.

640460666 is a deficient number, since it is larger than the sum of its proper divisors (320230336).

640460666 is a wasteful number, since it uses less digits than its factorization.

640460666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320230335.

The product of its (nonzero) digits is 124416, while the sum is 38.

The square root of 640460666 is about 25307.3243548187. The cubic root of 640460666 is about 861.9805920089.

The spelling of 640460666 in words is "six hundred forty million, four hundred sixty thousand, six hundred sixty-six".