640235648 has 32 divisors (see below), whose sum is σ = 1373586060. Its totient is φ = 295492608.

The previous prime is 640235641. The next prime is 640235663. The reversal of 640235648 is 846532046.

It can be written as a sum of positive squares in 2 ways, for example, as 594969664 + 45265984 = 24392^2 + 6728^2 .

It is a tau number, because it is divible by the number of its divisors (32).

It is not an unprimeable number, because it can be changed into a prime (640235641) 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, 190715 + ... + 194042.

Almost surely, 2^640235648 is an apocalyptic number.

It is an amenable number.

640235648 is an abundant number, since it is smaller than the sum of its proper divisors (733350412).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640235648 is a wasteful number, since it uses less digits than its factorization.

640235648 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 384784 (or 384772 counting only the distinct ones).

The product of its (nonzero) digits is 138240, while the sum is 38.

The square root of 640235648 is about 25302.8782552499. The cubic root of 640235648 is about 861.8796314145.

The spelling of 640235648 in words is "six hundred forty million, two hundred thirty-five thousand, six hundred forty-eight".