16660561 has 6 divisors (see below), whose sum is σ = 17698550. Its totient is φ = 15680256.

The previous prime is 16660543. The next prime is 16660577. The reversal of 16660561 is 16506661.

It can be written as a sum of positive squares in 3 ways, for example, as 12559936 + 4100625 = 3544^2 + 2025^2 .

It is not a de Polignac number, because 16660561 - 2¹¹ = 16658513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16660531) 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 5 ways as a sum of consecutive naturals, for example, 28536 + ... + 29113.

Almost surely, 2^16660561 is an apocalyptic number.

It is an amenable number.

16660561 is a deficient number, since it is larger than the sum of its proper divisors (1037989).

16660561 is an equidigital number, since it uses as much as digits as its factorization.

16660561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57683 (or 57666 counting only the distinct ones).

The product of its (nonzero) digits is 6480, while the sum is 31.

The square root of 16660561 is about 4081.7350477462. The cubic root of 16660561 is about 255.4052814550.

The spelling of 16660561 in words is "sixteen million, six hundred sixty thousand, five hundred sixty-one".