20569009561 has 3 divisors (see below), whose sum is σ = 20569152981. Its totient is φ = 20568866142.

The previous prime is 20569009541. The next prime is 20569009567. The reversal of 20569009561 is 16590096502.

The square root of 20569009561 is 143419.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is not a de Polignac number, because 20569009561 - 2⁹ = 20569009049 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20569009567) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 71710 + ... + 215128.

It is an arithmetic number, because the mean of its divisors is an integer number (6856384327).

Almost surely, 2^20569009561 is an apocalyptic number.

20569009561 is the 143419-th square number.

20569009561 is the 71710-th centered octagonal number.

It is an amenable number.

20569009561 is a deficient number, since it is larger than the sum of its proper divisors (143420).

20569009561 is an frugal number, since it uses more digits than its factorization.

20569009561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 286838 (or 143419 counting only the distinct ones).

The product of its (nonzero) digits is 145800, while the sum is 43.

The spelling of 20569009561 in words is "twenty billion, five hundred sixty-nine million, nine thousand, five hundred sixty-one".