16665621 has 8 divisors (see below), whose sum is σ = 25395264. Its totient is φ = 9523200.

The previous prime is 16665619. The next prime is 16665629. The reversal of 16665621 is 12656661.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 16665621 - 2¹ = 16665619 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16665629) 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 7 ways as a sum of consecutive naturals, for example, 396780 + ... + 396821.

It is an arithmetic number, because the mean of its divisors is an integer number (3174408).

Almost surely, 2^16665621 is an apocalyptic number.

It is an amenable number.

16665621 is a deficient number, since it is larger than the sum of its proper divisors (8729643).

16665621 is an equidigital number, since it uses as much as digits as its factorization.

16665621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 793611.

The product of its digits is 12960, while the sum is 33.

The square root of 16665621 is about 4082.3548351411. The cubic root of 16665621 is about 255.4311353246.

The spelling of 16665621 in words is "sixteen million, six hundred sixty-five thousand, six hundred twenty-one".