16817981 has 4 divisors (see below), whose sum is σ = 17807292. Its totient is φ = 15828672.

The previous prime is 16817953. The next prime is 16817987. The reversal of 16817981 is 18971861.

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 9821956 + 6996025 = 3134^2 + 2645^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16817981 is a prime.

It is a super-2 number, since 2×16817981² = 565688969832722, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16817987) 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, 494630 + ... + 494663.

It is an arithmetic number, because the mean of its divisors is an integer number (4451823).

Almost surely, 2^16817981 is an apocalyptic number.

It is an amenable number.

16817981 is a deficient number, since it is larger than the sum of its proper divisors (989311).

16817981 is an equidigital number, since it uses as much as digits as its factorization.

16817981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 989310.

The product of its digits is 24192, while the sum is 41.

The square root of 16817981 is about 4100.9731771861. The cubic root of 16817981 is about 256.2071738067.

The spelling of 16817981 in words is "sixteen million, eight hundred seventeen thousand, nine hundred eighty-one".