643994928 has 40 divisors (see below), whose sum is σ = 1848505200. Its totient is φ = 214664832.

The previous prime is 643994881. The next prime is 643994933. The reversal of 643994928 is 829499346.

643994928 is a `hidden beast` number, since 64 + 3 + 99 + 492 + 8 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a nude number because it is divisible by every one of its digits.

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, 744933 + ... + 745796.

It is an arithmetic number, because the mean of its divisors is an integer number (46212630).

Almost surely, 2^643994928 is an apocalyptic number.

It is an amenable number.

643994928 is an abundant number, since it is smaller than the sum of its proper divisors (1204510272).

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

643994928 is a wasteful number, since it uses less digits than its factorization.

643994928 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1490746 (or 1490734 counting only the distinct ones).

The product of its digits is 3359232, while the sum is 54.

The square root of 643994928 is about 25377.0551483028. The cubic root of 643994928 is about 863.5632437610.

The spelling of 643994928 in words is "six hundred forty-three million, nine hundred ninety-four thousand, nine hundred twenty-eight".