643920399 has 12 divisors (see below), whose sum is σ = 951738216. Its totient is φ = 419296752.

The previous prime is 643920383. The next prime is 643920461. The reversal of 643920399 is 993029346.

643920399 is a `hidden beast` number, since 6 + 439 + 203 + 9 + 9 = 666.

It is not a de Polignac number, because 643920399 - 2⁴ = 643920383 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643928399) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 831552 + ... + 832325.

It is an arithmetic number, because the mean of its divisors is an integer number (79311518).

Almost surely, 2^643920399 is an apocalyptic number.

643920399 is a deficient number, since it is larger than the sum of its proper divisors (307817817).

643920399 is a wasteful number, since it uses less digits than its factorization.

643920399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1663926 (or 1663923 counting only the distinct ones).

The product of its (nonzero) digits is 314928, while the sum is 45.

The square root of 643920399 is about 25375.5866730210. The cubic root of 643920399 is about 863.5299293226.

The spelling of 643920399 in words is "six hundred forty-three million, nine hundred twenty thousand, three hundred ninety-nine".