16656581 has 2 divisors, whose sum is σ = 16656582. Its totient is φ = 16656580.

The previous prime is 16656571. The next prime is 16656593. The reversal of 16656581 is 18565661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12716356 + 3940225 = 3566^2 + 1985^2 .

It is a cyclic number.

It is not a de Polignac number, because 16656581 - 2²² = 12462277 is a prime.

It is a super-2 number, since 2×16656581² = 554883381219122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16656571) 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, 8328290 + 8328291.

It is an arithmetic number, because the mean of its divisors is an integer number (8328291).

Almost surely, 2^16656581 is an apocalyptic number.

It is an amenable number.

16656581 is a deficient number, since it is larger than the sum of its proper divisors (1).

16656581 is an equidigital number, since it uses as much as digits as its factorization.

16656581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 43200, while the sum is 38.

The square root of 16656581 is about 4081.2474808568. The cubic root of 16656581 is about 255.3849421244.

The spelling of 16656581 in words is "sixteen million, six hundred fifty-six thousand, five hundred eighty-one".