16981581 has 4 divisors (see below), whose sum is σ = 22642112. Its totient is φ = 11321052.

The previous prime is 16981577. The next prime is 16981609. The reversal of 16981581 is 18518961.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 18518961 = 3 ⋅6172987.

It is not a de Polignac number, because 16981581 - 2² = 16981577 is a prime.

It is a super-2 number, since 2×16981581² = 576748186519122, 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 (16981511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2830261 + ... + 2830266.

It is an arithmetic number, because the mean of its divisors is an integer number (5660528).

Almost surely, 2^16981581 is an apocalyptic number.

It is an amenable number.

16981581 is a deficient number, since it is larger than the sum of its proper divisors (5660531).

16981581 is an equidigital number, since it uses as much as digits as its factorization.

16981581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5660530.

The product of its digits is 17280, while the sum is 39.

The square root of 16981581 is about 4120.8713884323. The cubic root of 16981581 is about 257.0352619080.

The spelling of 16981581 in words is "sixteen million, nine hundred eighty-one thousand, five hundred eighty-one".