643634729 has 8 divisors (see below), whose sum is σ = 676746120. Its totient is φ = 611251200.

The previous prime is 643634723. The next prime is 643634749. The reversal of 643634729 is 927436346.

It can be written as a sum of positive squares in 4 ways, for example, as 30824704 + 612810025 = 5552^2 + 24755^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 643634729 - 2⁴ = 643634713 is a prime.

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 643634729.

It is not an unprimeable number, because it can be changed into a prime (643634723) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 180152 + ... + 183689.

It is an arithmetic number, because the mean of its divisors is an integer number (84593265).

Almost surely, 2^643634729 is an apocalyptic number.

It is an amenable number.

643634729 is a deficient number, since it is larger than the sum of its proper divisors (33111391).

643634729 is a wasteful number, since it uses less digits than its factorization.

643634729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 363931.

The product of its digits is 653184, while the sum is 44.

The square root of 643634729 is about 25369.9572132079. The cubic root of 643634729 is about 863.4022111118.

The spelling of 643634729 in words is "six hundred forty-three million, six hundred thirty-four thousand, seven hundred twenty-nine".