20556609 has 4 divisors (see below), whose sum is σ = 27408816. Its totient is φ = 13704404.

The previous prime is 20556607. The next prime is 20556617. The reversal of 20556609 is 90665502.

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 a cyclic number.

It is not a de Polignac number, because 20556609 - 2¹ = 20556607 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20556609.

It is not an unprimeable number, because it can be changed into a prime (20556607) 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, 3426099 + ... + 3426104.

It is an arithmetic number, because the mean of its divisors is an integer number (6852204).

Almost surely, 2^20556609 is an apocalyptic number.

It is an amenable number.

20556609 is a deficient number, since it is larger than the sum of its proper divisors (6852207).

20556609 is an equidigital number, since it uses as much as digits as its factorization.

20556609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6852206.

The product of its (nonzero) digits is 16200, while the sum is 33.

The square root of 20556609 is about 4533.9396775873. The cubic root of 20556609 is about 273.9368716342.

Adding to 20556609 its reverse (90665502), we get a palindrome (111222111).

The spelling of 20556609 in words is "twenty million, five hundred fifty-six thousand, six hundred nine".