16680781 has 4 divisors (see below), whose sum is σ = 17963932. Its totient is φ = 15397632.

The previous prime is 16680767. The next prime is 16680787. The reversal of 16680781 is 18708661.

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 9030025 + 7650756 = 3005^2 + 2766^2 .

It is a cyclic number.

It is not a de Polignac number, because 16680781 - 2¹¹ = 16678733 is a prime.

It is a super-2 number, since 2×16680781² = 556496909539922, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 16680781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16680787) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 641556 + ... + 641581.

It is an arithmetic number, because the mean of its divisors is an integer number (4490983).

Almost surely, 2^16680781 is an apocalyptic number.

It is an amenable number.

16680781 is a deficient number, since it is larger than the sum of its proper divisors (1283151).

16680781 is a wasteful number, since it uses less digits than its factorization.

16680781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1283150.

The product of its (nonzero) digits is 16128, while the sum is 37.

The square root of 16680781 is about 4084.2111845496. The cubic root of 16680781 is about 255.5085634312.

The spelling of 16680781 in words is "sixteen million, six hundred eighty thousand, seven hundred eighty-one".