16661405 has 4 divisors (see below), whose sum is σ = 19993692. Its totient is φ = 13329120.

The previous prime is 16661401. The next prime is 16661417. The reversal of 16661405 is 50416661.

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 12243001 + 4418404 = 3499^2 + 2102^2 .

It is not a de Polignac number, because 16661405 - 2² = 16661401 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16661401) 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, 1666136 + ... + 1666145.

It is an arithmetic number, because the mean of its divisors is an integer number (4998423).

Almost surely, 2^16661405 is an apocalyptic number.

It is an amenable number.

16661405 is a deficient number, since it is larger than the sum of its proper divisors (3332287).

16661405 is an equidigital number, since it uses as much as digits as its factorization.

16661405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3332286.

The product of its (nonzero) digits is 4320, while the sum is 29.

The square root of 16661405 is about 4081.8384338433. The cubic root of 16661405 is about 255.4095942033.

The spelling of 16661405 in words is "sixteen million, six hundred sixty-one thousand, four hundred five".