643845726509 has 4 divisors (see below), whose sum is σ = 643961469216. Its totient is φ = 643729983804.

The previous prime is 643845726481. The next prime is 643845726541. The reversal of 643845726509 is 905627548346.

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.

It is a cyclic number.

It is not a de Polignac number, because 643845726509 - 2²⁴ = 643828949293 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 (643845726569) 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 3 ways as a sum of consecutive naturals, for example, 57863009 + ... + 57874134.

It is an arithmetic number, because the mean of its divisors is an integer number (160990367304).

Almost surely, 2^643845726509 is an apocalyptic number.

It is an amenable number.

643845726509 is a deficient number, since it is larger than the sum of its proper divisors (115742707).

643845726509 is a wasteful number, since it uses less digits than its factorization.

643845726509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 115742706.

The product of its (nonzero) digits is 43545600, while the sum is 59.

The spelling of 643845726509 in words is "six hundred forty-three billion, eight hundred forty-five million, seven hundred twenty-six thousand, five hundred nine".