643833985 has 4 divisors (see below), whose sum is σ = 772600788. Its totient is φ = 515067184.

The previous prime is 643833977. The next prime is 643833997. The reversal of 643833985 is 589338346.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 192016449 + 451817536 = 13857^2 + 21256^2 .

It is a cyclic number.

It is not a de Polignac number, because 643833985 - 2³ = 643833977 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64383394 + ... + 64383403.

It is an arithmetic number, because the mean of its divisors is an integer number (193150197).

Almost surely, 2^643833985 is an apocalyptic number.

It is an amenable number.

643833985 is a deficient number, since it is larger than the sum of its proper divisors (128766803).

643833985 is a wasteful number, since it uses less digits than its factorization.

643833985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128766802.

The product of its digits is 1866240, while the sum is 49.

The square root of 643833985 is about 25373.8839163420. The cubic root of 643833985 is about 863.4912990749.

The spelling of 643833985 in words is "six hundred forty-three million, eight hundred thirty-three thousand, nine hundred eighty-five".