643965680 has 40 divisors (see below), whose sum is σ = 1533745584. Its totient is φ = 251302400.

The previous prime is 643965607. The next prime is 643965683. The reversal of 643965680 is 86569346.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643965683) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 94886 + ... + 101445.

Almost surely, 2^643965680 is an apocalyptic number.

It is an amenable number.

643965680 is an abundant number, since it is smaller than the sum of its proper divisors (889779904).

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

643965680 is a wasteful number, since it uses less digits than its factorization.

643965680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 196385 (or 196379 counting only the distinct ones).

The product of its (nonzero) digits is 933120, while the sum is 47.

The square root of 643965680 is about 25376.4788731613. The cubic root of 643965680 is about 863.5501702211.

The spelling of 643965680 in words is "six hundred forty-three million, nine hundred sixty-five thousand, six hundred eighty".