20005609 has 4 divisors (see below), whose sum is σ = 21544516. Its totient is φ = 18466704.

The previous prime is 20005603. The next prime is 20005637. The reversal of 20005609 is 90650002.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90650002 = 2 ⋅45325001.

It can be written as a sum of positive squares in 2 ways, for example, as 1755625 + 18249984 = 1325^2 + 4272^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20005609 is a prime.

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 20005609.

It is not an unprimeable number, because it can be changed into a prime (20005603) 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, 769434 + ... + 769459.

It is an arithmetic number, because the mean of its divisors is an integer number (5386129).

Almost surely, 2^20005609 is an apocalyptic number.

It is an amenable number.

20005609 is a deficient number, since it is larger than the sum of its proper divisors (1538907).

20005609 is a wasteful number, since it uses less digits than its factorization.

20005609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1538906.

The product of its (nonzero) digits is 540, while the sum is 22.

The square root of 20005609 is about 4472.7630163021. The cubic root of 20005609 is about 271.4671345684.

The spelling of 20005609 in words is "twenty million, five thousand, six hundred nine".