16509891 has 4 divisors (see below), whose sum is σ = 22013192. Its totient is φ = 11006592.

The previous prime is 16509869. The next prime is 16509901. The reversal of 16509891 is 19890561.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 16509891 - 2⁵ = 16509859 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16509821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2751646 + ... + 2751651.

It is an arithmetic number, because the mean of its divisors is an integer number (5503298).

Almost surely, 2^16509891 is an apocalyptic number.

16509891 is a deficient number, since it is larger than the sum of its proper divisors (5503301).

16509891 is an equidigital number, since it uses as much as digits as its factorization.

16509891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5503300.

The product of its (nonzero) digits is 19440, while the sum is 39.

The square root of 16509891 is about 4063.2365178513. The cubic root of 16509891 is about 254.6330284676.

The spelling of 16509891 in words is "sixteen million, five hundred nine thousand, eight hundred ninety-one".