16566661 has 4 divisors (see below), whose sum is σ = 16580524. Its totient is φ = 16552800.

The previous prime is 16566637. The next prime is 16566691. The reversal of 16566661 is 16666561.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 14861025 + 1705636 = 3855^2 + 1306^2 .

It is a cyclic number.

It is not a de Polignac number, because 16566661 - 2¹⁵ = 16533893 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 16566661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16566611) 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 3 ways as a sum of consecutive naturals, for example, 4950 + ... + 7591.

It is an arithmetic number, because the mean of its divisors is an integer number (4145131).

Almost surely, 2^16566661 is an apocalyptic number.

It is an amenable number.

16566661 is a deficient number, since it is larger than the sum of its proper divisors (13863).

16566661 is a wasteful number, since it uses less digits than its factorization.

16566661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13862.

The product of its digits is 38880, while the sum is 37.

The square root of 16566661 is about 4070.2163333169. The cubic root of 16566661 is about 254.9245502783.

The spelling of 16566661 in words is "sixteen million, five hundred sixty-six thousand, six hundred sixty-one".