643874509 has 4 divisors (see below), whose sum is σ = 643934304. Its totient is φ = 643814716.

The previous prime is 643874503. The next prime is 643874519. The reversal of 643874509 is 905478346.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 643874509 - 2¹⁵ = 643841741 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643874503) 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, 8767 + ... + 36940.

It is an arithmetic number, because the mean of its divisors is an integer number (160983576).

Almost surely, 2^643874509 is an apocalyptic number.

It is an amenable number.

643874509 is a deficient number, since it is larger than the sum of its proper divisors (59795).

643874509 is a wasteful number, since it uses less digits than its factorization.

643874509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59794.

The product of its (nonzero) digits is 725760, while the sum is 46.

The square root of 643874509 is about 25374.6824413627. The cubic root of 643874509 is about 863.5094152291.

The spelling of 643874509 in words is "six hundred forty-three million, eight hundred seventy-four thousand, five hundred nine".