643868844 has 48 divisors (see below), whose sum is σ = 1516636128. Its totient is φ = 212594688.

The previous prime is 643868843. The next prime is 643868867. The reversal of 643868844 is 448868346.

It is a hoax number, since the sum of its digits (51) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (643868843) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 733734 + ... + 734610.

It is an arithmetic number, because the mean of its divisors is an integer number (31596586).

Almost surely, 2^643868844 is an apocalyptic number.

It is an amenable number.

643868844 is an abundant number, since it is smaller than the sum of its proper divisors (872767284).

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

643868844 is a wasteful number, since it uses less digits than its factorization.

643868844 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1394 (or 1392 counting only the distinct ones).

The product of its digits is 3538944, while the sum is 51.

The square root of 643868844 is about 25374.5708141044. The cubic root of 643868844 is about 863.5068827505.

The spelling of 643868844 in words is "six hundred forty-three million, eight hundred sixty-eight thousand, eight hundred forty-four".