1644665465 has 4 divisors (see below), whose sum is σ = 1973598564. Its totient is φ = 1315732368.

The previous prime is 1644665461. The next prime is 1644665471. The reversal of 1644665465 is 5645664461.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5645664461 = 349 ⋅16176689.

It can be written as a sum of positive squares in 2 ways, for example, as 858255616 + 786409849 = 29296^2 + 28043^2 .

It is a cyclic number.

It is not a de Polignac number, because 1644665465 - 2² = 1644665461 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1644665461) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 164466542 + ... + 164466551.

It is an arithmetic number, because the mean of its divisors is an integer number (493399641).

Almost surely, 2^1644665465 is an apocalyptic number.

It is an amenable number.

1644665465 is a deficient number, since it is larger than the sum of its proper divisors (328933099).

1644665465 is an equidigital number, since it uses as much as digits as its factorization.

1644665465 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 328933098.

The product of its digits is 2073600, while the sum is 47.

The square root of 1644665465 is about 40554.4752770887. The cubic root of 1644665465 is about 1180.3909135260.

The spelling of 1644665465 in words is "one billion, six hundred forty-four million, six hundred sixty-five thousand, four hundred sixty-five".