16556661 has 24 divisors (see below), whose sum is σ = 26732160. Its totient is φ = 9787200.

The previous prime is 16556641. The next prime is 16556663. The reversal of 16556661 is 16665561.

It is not a de Polignac number, because 16556661 - 2⁵ = 16556629 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16556663) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2020 + ... + 6098.

It is an arithmetic number, because the mean of its divisors is an integer number (1113840).

Almost surely, 2^16556661 is an apocalyptic number.

16556661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

16556661 is a deficient number, since it is larger than the sum of its proper divisors (10175499).

16556661 is a wasteful number, since it uses less digits than its factorization.

16556661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4137 (or 4134 counting only the distinct ones).

The product of its digits is 32400, while the sum is 36.

The square root of 16556661 is about 4068.9877119500. The cubic root of 16556661 is about 254.8732472708.

Subtracting 16556661 from its reverse (16665561), we obtain a square (108900 = 330²).

The spelling of 16556661 in words is "sixteen million, five hundred fifty-six thousand, six hundred sixty-one".