16561611 has 16 divisors (see below), whose sum is σ = 26766720. Its totient is φ = 10037160.

The previous prime is 16561603. The next prime is 16561613. The reversal of 16561611 is 11616561.

16561611 is a `hidden beast` number, since 1 + 656 + 1 + 6 + 1 + 1 = 666.

It is not a de Polignac number, because 16561611 - 2³ = 16561603 is a prime.

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

It is not an unprimeable number, because it can be changed into a prime (16561613) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 27585 + ... + 28178.

It is an arithmetic number, because the mean of its divisors is an integer number (1672920).

Almost surely, 2^16561611 is an apocalyptic number.

16561611 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

16561611 is a deficient number, since it is larger than the sum of its proper divisors (10205109).

16561611 is a wasteful number, since it uses less digits than its factorization.

16561611 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55783 (or 55777 counting only the distinct ones).

The product of its digits is 1080, while the sum is 27.

The square root of 16561611 is about 4069.5959258875. The cubic root of 16561611 is about 254.8986448407.

It can be divided in two parts, 165 and 61611, that added together give a triangular number (61776 = T₃₅₁).

The spelling of 16561611 in words is "sixteen million, five hundred sixty-one thousand, six hundred eleven".