1645839905 has 4 divisors (see below), whose sum is σ = 1975007892. Its totient is φ = 1316671920.

The previous prime is 1645839889. The next prime is 1645839913. The reversal of 1645839905 is 5099385461.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5099385461 = 47 ⋅108497563.

It can be written as a sum of positive squares in 2 ways, for example, as 1232571664 + 413268241 = 35108^2 + 20329^2 .

It is not a de Polignac number, because 1645839905 - 2⁴ = 1645839889 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 164583986 + ... + 164583995.

It is an arithmetic number, because the mean of its divisors is an integer number (493751973).

Almost surely, 2^1645839905 is an apocalyptic number.

It is an amenable number.

1645839905 is a deficient number, since it is larger than the sum of its proper divisors (329167987).

1645839905 is an equidigital number, since it uses as much as digits as its factorization.

1645839905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 329167986.

The product of its (nonzero) digits is 1166400, while the sum is 50.

The square root of 1645839905 is about 40568.9524760007. The cubic root of 1645839905 is about 1180.6718153232.

The spelling of 1645839905 in words is "one billion, six hundred forty-five million, eight hundred thirty-nine thousand, nine hundred five".