1666021 has 12 divisors (see below), whose sum is σ = 1978912. Its totient is φ = 1373904.

The previous prime is 1666019. The next prime is 1666037. The reversal of 1666021 is 1206661.

It is not a de Polignac number, because 1666021 - 2¹ = 1666019 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1665983 and 1666001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1666061) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 5746 + ... + 6028.

2^1666021 is an apocalyptic number.

It is an amenable number.

1666021 is a deficient number, since it is larger than the sum of its proper divisors (312891).

1666021 is an equidigital number, since it uses as much as digits as its factorization.

1666021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 348 (or 319 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 1666021 is about 1290.7443588875. The cubic root of 1666021 is about 118.5477977225.

The spelling of 1666021 in words is "one million, six hundred sixty-six thousand, twenty-one".