643878065 has 8 divisors (see below), whose sum is σ = 781335720. Its totient is φ = 509314432.

The previous prime is 643878047. The next prime is 643878071. The reversal of 643878065 is 560878346.

It can be written as a sum of positive squares in 4 ways, for example, as 2421136 + 641456929 = 1556^2 + 25327^2 .

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 643878065 - 2¹⁶ = 643812529 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 723014 + ... + 723903.

It is an arithmetic number, because the mean of its divisors is an integer number (97666965).

Almost surely, 2^643878065 is an apocalyptic number.

It is an amenable number.

643878065 is a deficient number, since it is larger than the sum of its proper divisors (137457655).

643878065 is a wasteful number, since it uses less digits than its factorization.

643878065 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1447011.

The product of its (nonzero) digits is 967680, while the sum is 47.

The square root of 643878065 is about 25374.7525111084. The cubic root of 643878065 is about 863.5110048938.

The spelling of 643878065 in words is "six hundred forty-three million, eight hundred seventy-eight thousand, sixty-five".