1643889385 has 4 divisors (see below), whose sum is σ = 1972667268. Its totient is φ = 1315111504.

The previous prime is 1643889349. The next prime is 1643889413. The reversal of 1643889385 is 5839883461.

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 618865129 + 1025024256 = 24877^2 + 32016^2 .

It is a cyclic number.

It is not a de Polignac number, because 1643889385 - 2¹³ = 1643881193 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, 164388934 + ... + 164388943.

It is an arithmetic number, because the mean of its divisors is an integer number (493166817).

Almost surely, 2^1643889385 is an apocalyptic number.

It is an amenable number.

1643889385 is a deficient number, since it is larger than the sum of its proper divisors (328777883).

1643889385 is an equidigital number, since it uses as much as digits as its factorization.

1643889385 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 328777882.

The product of its digits is 4976640, while the sum is 55.

The square root of 1643889385 is about 40544.9057835877. The cubic root of 1643889385 is about 1180.2052178269.

The spelling of 1643889385 in words is "one billion, six hundred forty-three million, eight hundred eighty-nine thousand, three hundred eighty-five".