16609681 has 4 divisors (see below), whose sum is σ = 18119664. Its totient is φ = 15099700.

The previous prime is 16609673. The next prime is 16609687. The reversal of 16609681 is 18690661.

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.

It is not a de Polignac number, because 16609681 - 2³ = 16609673 is a prime.

It is a super-2 number, since 2×16609681² = 551763005843522, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 16609681.

It is not an unprimeable number, because it can be changed into a prime (16609687) 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, 754975 + ... + 754996.

It is an arithmetic number, because the mean of its divisors is an integer number (4529916).

Almost surely, 2^16609681 is an apocalyptic number.

16609681 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

16609681 is a deficient number, since it is larger than the sum of its proper divisors (1509983).

16609681 is a wasteful number, since it uses less digits than its factorization.

16609681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1509982.

The product of its (nonzero) digits is 15552, while the sum is 37.

The square root of 16609681 is about 4075.4976383259. The cubic root of 16609681 is about 255.1450206753.

The spelling of 16609681 in words is "sixteen million, six hundred nine thousand, six hundred eighty-one".