640649907 has 12 divisors (see below), whose sum is σ = 941068440. Its totient is φ = 419860608.

The previous prime is 640649899. The next prime is 640649929. The reversal of 640649907 is 709946046.

It is not a de Polignac number, because 640649907 - 2³ = 640649899 is a prime.

It is not an unprimeable number, because it can be changed into a prime (640649957) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 602718 + ... + 603779.

It is an arithmetic number, because the mean of its divisors is an integer number (78422370).

Almost surely, 2^640649907 is an apocalyptic number.

640649907 is a deficient number, since it is larger than the sum of its proper divisors (300418533).

640649907 is a wasteful number, since it uses less digits than its factorization.

640649907 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1206562 (or 1206559 counting only the distinct ones).

The product of its (nonzero) digits is 326592, while the sum is 45.

The square root of 640649907 is about 25311.0629369847. The cubic root of 640649907 is about 862.0654819505.

The spelling of 640649907 in words is "six hundred forty million, six hundred forty-nine thousand, nine hundred seven".