643918816 has 24 divisors (see below), whose sum is σ = 1334438280. Its totient is φ = 305013888.

The previous prime is 643918811. The next prime is 643918853. The reversal of 643918816 is 618819346.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643918811) 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, 528931 + ... + 530146.

It is an arithmetic number, because the mean of its divisors is an integer number (55601595).

Almost surely, 2^643918816 is an apocalyptic number.

It is an amenable number.

643918816 is an abundant number, since it is smaller than the sum of its proper divisors (690519464).

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

643918816 is a wasteful number, since it uses less digits than its factorization.

643918816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1059106 (or 1059098 counting only the distinct ones).

The product of its digits is 248832, while the sum is 46.

The square root of 643918816 is about 25375.5554816047. Note that the first 3 decimals coincide. The cubic root of 643918816 is about 863.5292216943.

The spelling of 643918816 in words is "six hundred forty-three million, nine hundred eighteen thousand, eight hundred sixteen".