20561305 has 4 divisors (see below), whose sum is σ = 24673572. Its totient is φ = 16449040.

The previous prime is 20561291. The next prime is 20561311. The reversal of 20561305 is 50316502.

It is a happy number.

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 11964681 + 8596624 = 3459^2 + 2932^2 .

It is not a de Polignac number, because 20561305 - 2⁵ = 20561273 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2056126 + ... + 2056135.

It is an arithmetic number, because the mean of its divisors is an integer number (6168393).

Almost surely, 2^20561305 is an apocalyptic number.

It is an amenable number.

20561305 is a deficient number, since it is larger than the sum of its proper divisors (4112267).

20561305 is an equidigital number, since it uses as much as digits as its factorization.

20561305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4112266.

The product of its (nonzero) digits is 900, while the sum is 22.

The square root of 20561305 is about 4534.4575199245. The cubic root of 20561305 is about 273.9577296399.

Adding to 20561305 its reverse (50316502), we get a palindrome (70877807).

The spelling of 20561305 in words is "twenty million, five hundred sixty-one thousand, three hundred five".