643511659 has 24 divisors (see below), whose sum is σ = 814069440. Its totient is φ = 505080576.

The previous prime is 643511633. The next prime is 643511663. The reversal of 643511659 is 956115346.

It is a happy number.

It is not a de Polignac number, because 643511659 - 2¹³ = 643503467 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643511689) 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 23 ways as a sum of consecutive naturals, for example, 20382 + ... + 41260.

It is an arithmetic number, because the mean of its divisors is an integer number (33919560).

Almost surely, 2^643511659 is an apocalyptic number.

643511659 is a deficient number, since it is larger than the sum of its proper divisors (170557781).

643511659 is a wasteful number, since it uses less digits than its factorization.

643511659 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20947 (or 20940 counting only the distinct ones).

The product of its digits is 97200, while the sum is 40.

The square root of 643511659 is about 25367.5315905982. The cubic root of 643511659 is about 863.3471769552.

The spelling of 643511659 in words is "six hundred forty-three million, five hundred eleven thousand, six hundred fifty-nine".