16816981 has 4 divisors (see below), whose sum is σ = 17271532. Its totient is φ = 16362432.

The previous prime is 16816951. The next prime is 16816991. The reversal of 16816981 is 18961861.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18961861 = 587 ⋅32303.

It can be written as a sum of positive squares in 2 ways, for example, as 12716356 + 4100625 = 3566^2 + 2025^2 .

It is a cyclic number.

It is not a de Polignac number, because 16816981 - 2⁹ = 16816469 is a prime.

It is a super-2 number, since 2×16816981² = 565621699908722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16816931) 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, 227220 + ... + 227293.

It is an arithmetic number, because the mean of its divisors is an integer number (4317883).

Almost surely, 2^16816981 is an apocalyptic number.

It is an amenable number.

16816981 is a deficient number, since it is larger than the sum of its proper divisors (454551).

16816981 is an equidigital number, since it uses as much as digits as its factorization.

16816981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 454550.

The product of its digits is 20736, while the sum is 40.

The square root of 16816981 is about 4100.8512530937. The cubic root of 16816981 is about 256.2020956654.

The spelling of 16816981 in words is "sixteen million, eight hundred sixteen thousand, nine hundred eighty-one".