20635609 has 4 divisors (see below), whose sum is σ = 20767204. Its totient is φ = 20504016.

The previous prime is 20635597. The next prime is 20635627. The reversal of 20635609 is 90653602.

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

It can be written as a sum of positive squares in 2 ways, for example, as 7997584 + 12638025 = 2828^2 + 3555^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20635609 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20635649) 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, 65562 + ... + 65875.

It is an arithmetic number, because the mean of its divisors is an integer number (5191801).

Almost surely, 2^20635609 is an apocalyptic number.

It is an amenable number.

20635609 is a deficient number, since it is larger than the sum of its proper divisors (131595).

20635609 is a wasteful number, since it uses less digits than its factorization.

20635609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 131594.

The product of its (nonzero) digits is 9720, while the sum is 31.

The square root of 20635609 is about 4542.6433934440. The cubic root of 20635609 is about 274.2873404206.

The spelling of 20635609 in words is "twenty million, six hundred thirty-five thousand, six hundred nine".