640257680 has 40 divisors (see below), whose sum is σ = 1490529600. Its totient is φ = 255771008.

The previous prime is 640257677. The next prime is 640257697. The reversal of 640257680 is 86752046.

It is a happy number.

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

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 62351 + ... + 71889.

It is an arithmetic number, because the mean of its divisors is an integer number (37263240).

Almost surely, 2^640257680 is an apocalyptic number.

It is an amenable number.

640257680 is an abundant number, since it is smaller than the sum of its proper divisors (850271920).

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

640257680 is a wasteful number, since it uses less digits than its factorization.

640257680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10391 (or 10385 counting only the distinct ones).

The product of its (nonzero) digits is 80640, while the sum is 38.

The square root of 640257680 is about 25303.3136169949. The cubic root of 640257680 is about 861.8895177297.

The spelling of 640257680 in words is "six hundred forty million, two hundred fifty-seven thousand, six hundred eighty".