16665021 has 20 divisors (see below), whose sum is σ = 25016992. Its totient is φ = 11055528.

The previous prime is 16665001. The next prime is 16665023. The reversal of 16665021 is 12056661.

It is a happy number.

It is not a de Polignac number, because 16665021 - 2¹⁴ = 16648637 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16665023) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 22560 + ... + 23286.

Almost surely, 2^16665021 is an apocalyptic number.

It is an amenable number.

16665021 is a deficient number, since it is larger than the sum of its proper divisors (8351971).

16665021 is an equidigital number, since it uses as much as digits as its factorization.

16665021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1022 (or 1013 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 16665021 is about 4082.2813474821. The cubic root of 16665021 is about 255.4280699219.

The spelling of 16665021 in words is "sixteen million, six hundred sixty-five thousand, twenty-one".