640715440 has 40 divisors (see below), whose sum is σ = 1537723008. Its totient is φ = 248017920.

The previous prime is 640715423. The next prime is 640715443. The reversal of 640715440 is 44517046.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (31).

It is not an unprimeable number, because it can be changed into a prime (640715443) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 126697 + ... + 131656.

Almost surely, 2^640715440 is an apocalyptic number.

It is an amenable number.

640715440 is an abundant number, since it is smaller than the sum of its proper divisors (897007568).

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

640715440 is a wasteful number, since it uses less digits than its factorization.

640715440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 258397 (or 258391 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 31.

The square root of 640715440 is about 25312.3574563888. The cubic root of 640715440 is about 862.0948749208.

The spelling of 640715440 in words is "six hundred forty million, seven hundred fifteen thousand, four hundred forty".