16657681 has 6 divisors (see below), whose sum is σ = 17413970. Its totient is φ = 15932928.

The previous prime is 16657657. The next prime is 16657691. The reversal of 16657681 is 18675661.

It can be written as a sum of positive squares in only one way, i.e., 14753281 + 1904400 = 3841^2 + 1380^2 .

It is not a de Polignac number, because 16657681 - 2⁹ = 16657169 is a prime.

It is a super-2 number, since 2×16657681² = 554956672595522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16657601) 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, 15216 + ... + 16273.

Almost surely, 2^16657681 is an apocalyptic number.

It is an amenable number.

16657681 is a deficient number, since it is larger than the sum of its proper divisors (756289).

16657681 is an equidigital number, since it uses as much as digits as its factorization.

16657681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31535 (or 31512 counting only the distinct ones).

The product of its digits is 60480, while the sum is 40.

The square root of 16657681 is about 4081.3822413491. The cubic root of 16657681 is about 255.3905638714.

The spelling of 16657681 in words is "sixteen million, six hundred fifty-seven thousand, six hundred eighty-one".