643673923 has 18 divisors (see below), whose sum is σ = 680626716. Its totient is φ = 608392512.

The previous prime is 643673903. The next prime is 643673951. The reversal of 643673923 is 329376346.

It is not a de Polignac number, because 643673923 - 2²⁵ = 610119491 is a prime.

It is a super-2 number, since 2×643673923² = 828632238300419858, which contains 22 as substring.

It is a Smith number, since the sum of its digits (43) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (43).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 643673923.

It is not an unprimeable number, because it can be changed into a prime (643673903) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 8817415 + ... + 8817487.

Almost surely, 2^643673923 is an apocalyptic number.

643673923 is a deficient number, since it is larger than the sum of its proper divisors (36952793).

643673923 is an frugal number, since it uses more digits than its factorization.

643673923 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 295 (or 169 counting only the distinct ones).

The product of its digits is 489888, while the sum is 43.

The square root of 643673923 is about 25370.7296505244. The cubic root of 643673923 is about 863.4197363208.

Multiplying 643673923 by its sum of digits (43), we get a square (27677978689 = 166367²).

643673923 divided by its sum of digits (43) gives a square (14969161 = 3869²).

The spelling of 643673923 in words is "six hundred forty-three million, six hundred seventy-three thousand, nine hundred twenty-three".