1644536665 has 8 divisors (see below), whose sum is σ = 1988509248. Its totient is φ = 1305585840.

The previous prime is 1644536651. The next prime is 1644536693. The reversal of 1644536665 is 5666354461.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1644536665 - 2¹⁷ = 1644405593 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 (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1254717 + ... + 1256026.

It is an arithmetic number, because the mean of its divisors is an integer number (248563656).

Almost surely, 2^1644536665 is an apocalyptic number.

It is an amenable number.

1644536665 is a deficient number, since it is larger than the sum of its proper divisors (343972583).

1644536665 is a wasteful number, since it uses less digits than its factorization.

1644536665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2510879.

The product of its digits is 1555200, while the sum is 46.

The square root of 1644536665 is about 40552.8872584925. The cubic root of 1644536665 is about 1180.3600990895.

The spelling of 1644536665 in words is "one billion, six hundred forty-four million, five hundred thirty-six thousand, six hundred sixty-five".