1646665 has 4 divisors (see below), whose sum is σ = 1976004. Its totient is φ = 1317328.

The previous prime is 1646647. The next prime is 1646669. The reversal of 1646665 is 5666461.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5666461 = 47 ⋅120563.

It can be written as a sum of positive squares in 2 ways, for example, as 622521 + 1024144 = 789^2 + 1012^2 .

It is a cyclic number.

It is not a de Polignac number, because 1646665 - 2⁵ = 1646633 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1646665.

It is not an unprimeable number, because it can be changed into a prime (1646669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 164662 + ... + 164671.

It is an arithmetic number, because the mean of its divisors is an integer number (494001).

2^1646665 is an apocalyptic number.

It is an amenable number.

1646665 is a deficient number, since it is larger than the sum of its proper divisors (329339).

1646665 is an equidigital number, since it uses as much as digits as its factorization.

1646665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 329338.

The product of its digits is 25920, while the sum is 34.

The square root of 1646665 is about 1283.2244542558. The cubic root of 1646665 is about 118.0869081101.

The spelling of 1646665 in words is "one million, six hundred forty-six thousand, six hundred sixty-five".