16509905 has 4 divisors (see below), whose sum is σ = 19811892. Its totient is φ = 13207920.

The previous prime is 16509901. The next prime is 16509919. The reversal of 16509905 is 50990561.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 50990561 = 43 ⋅1185827.

It can be written as a sum of positive squares in 2 ways, for example, as 6115729 + 10394176 = 2473^2 + 3224^2 .

It is not a de Polignac number, because 16509905 - 2² = 16509901 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16509901) 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, 1650986 + ... + 1650995.

It is an arithmetic number, because the mean of its divisors is an integer number (4952973).

Almost surely, 2^16509905 is an apocalyptic number.

It is an amenable number.

16509905 is a deficient number, since it is larger than the sum of its proper divisors (3301987).

16509905 is an equidigital number, since it uses as much as digits as its factorization.

16509905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3301986.

The product of its (nonzero) digits is 12150, while the sum is 35.

The square root of 16509905 is about 4063.2382406155. The cubic root of 16509905 is about 254.6331004419.

The spelling of 16509905 in words is "sixteen million, five hundred nine thousand, nine hundred five".