640625668 has 12 divisors (see below), whose sum is σ = 1125992140. Its totient is φ = 318913632.

The previous prime is 640625663. The next prime is 640625677. The reversal of 640625668 is 866526046.

It can be written as a sum of positive squares in 2 ways, for example, as 534164544 + 106461124 = 23112^2 + 10318^2 .

It is not an unprimeable number, because it can be changed into a prime (640625663) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 348771 + ... + 350602.

Almost surely, 2^640625668 is an apocalyptic number.

It is an amenable number.

640625668 is a deficient number, since it is larger than the sum of its proper divisors (485366472).

640625668 is a wasteful number, since it uses less digits than its factorization.

640625668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 699606 (or 699604 counting only the distinct ones).

The product of its (nonzero) digits is 414720, while the sum is 43.

The square root of 640625668 is about 25310.5841102097. The cubic root of 640625668 is about 862.0546097260.

The spelling of 640625668 in words is "six hundred forty million, six hundred twenty-five thousand, six hundred sixty-eight".