1644664005 has 24 divisors (see below), whose sum is σ = 2897489400. Its totient is φ = 862773120.

The previous prime is 1644663989. The next prime is 1644664027. The reversal of 1644664005 is 5004664461.

1644664005 is a `hidden beast` number, since 1 + 6 + 4 + 4 + 6 + 640 + 0 + 5 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 108180801 + 1536483204 = 10401^2 + 39198^2 .

It is not a de Polignac number, because 1644664005 - 2⁴ = 1644663989 is a prime.

It is a congruent number.

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 23 ways as a sum of consecutive naturals, for example, 296830 + ... + 302319.

It is an arithmetic number, because the mean of its divisors is an integer number (120728725).

Almost surely, 2^1644664005 is an apocalyptic number.

1644664005 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1644664005 is a deficient number, since it is larger than the sum of its proper divisors (1252825395).

1644664005 is a wasteful number, since it uses less digits than its factorization.

1644664005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 599221 (or 599218 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 36.

The square root of 1644664005 is about 40554.4572766052. The cubic root of 1644664005 is about 1180.3905642410.

The spelling of 1644664005 in words is "one billion, six hundred forty-four million, six hundred sixty-four thousand, five".