1665985 has 4 divisors (see below), whose sum is σ = 1999188. Its totient is φ = 1332784.

The previous prime is 1665973. The next prime is 1665997. The reversal of 1665985 is 5895661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5895661 = 281 ⋅20981.

It is an interprime number because it is at equal distance from previous prime (1665973) and next prime (1665997).

It can be written as a sum of positive squares in 2 ways, for example, as 1181569 + 484416 = 1087^2 + 696^2 .

It is a cyclic number.

It is not a de Polignac number, because 1665985 - 2¹³ = 1657793 is a prime.

It is a Duffinian number.

1665985 is a lucky 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, 166594 + ... + 166603.

It is an arithmetic number, because the mean of its divisors is an integer number (499797).

2^1665985 is an apocalyptic number.

It is an amenable number.

1665985 is a deficient number, since it is larger than the sum of its proper divisors (333203).

1665985 is an equidigital number, since it uses as much as digits as its factorization.

1665985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 333202.

The product of its digits is 64800, while the sum is 40.

The square root of 1665985 is about 1290.7304133707. The cubic root of 1665985 is about 118.5469438414.

The spelling of 1665985 in words is "one million, six hundred sixty-five thousand, nine hundred eighty-five".