16643661 has 4 divisors (see below), whose sum is σ = 22191552. Its totient is φ = 11095772.

The previous prime is 16643659. The next prime is 16643707. The reversal of 16643661 is 16634661.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 16643661 - 2¹ = 16643659 is a prime.

It is a super-2 number, since 2×16643661² = 554022902965842, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16643611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2773941 + ... + 2773946.

It is an arithmetic number, because the mean of its divisors is an integer number (5547888).

Almost surely, 2^16643661 is an apocalyptic number.

It is an amenable number.

16643661 is a deficient number, since it is larger than the sum of its proper divisors (5547891).

16643661 is an equidigital number, since it uses as much as digits as its factorization.

16643661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5547890.

The product of its digits is 15552, while the sum is 33.

The square root of 16643661 is about 4079.6643244267. The cubic root of 16643661 is about 255.3188936169.

The spelling of 16643661 in words is "sixteen million, six hundred forty-three thousand, six hundred sixty-one".