16681666 has 4 divisors (see below), whose sum is σ = 25022502. Its totient is φ = 8340832.

The previous prime is 16681661. The next prime is 16681667. The reversal of 16681666 is 66618661.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 8439025 + 8242641 = 2905^2 + 2871^2 .

It is not an unprimeable number, because it can be changed into a prime (16681661) 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 as a sum of consecutive naturals, namely, 4170415 + ... + 4170418.

Almost surely, 2^16681666 is an apocalyptic number.

16681666 is a deficient number, since it is larger than the sum of its proper divisors (8340836).

16681666 is an equidigital number, since it uses as much as digits as its factorization.

16681666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8340835.

The product of its digits is 62208, while the sum is 40.

The square root of 16681666 is about 4084.3195271673. The cubic root of 16681666 is about 255.5130820262.

The spelling of 16681666 in words is "sixteen million, six hundred eighty-one thousand, six hundred sixty-six".