20561605705 has 8 divisors (see below), whose sum is σ = 24686917704. Its totient is φ = 16440624000.

The previous prime is 20561605651. The next prime is 20561605783. The reversal of 20561605705 is 50750616502.

It can be written as a sum of positive squares in 4 ways, for example, as 310323456 + 20251282249 = 17616^2 + 142307^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20561605705 - 2⁷ = 20561605577 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1072116 + ... + 1091125.

It is an arithmetic number, because the mean of its divisors is an integer number (3085864713).

Almost surely, 2^20561605705 is an apocalyptic number.

It is an amenable number.

20561605705 is a deficient number, since it is larger than the sum of its proper divisors (4125311999).

20561605705 is a wasteful number, since it uses less digits than its factorization.

20561605705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2165147.

The product of its (nonzero) digits is 63000, while the sum is 37.

The spelling of 20561605705 in words is "twenty billion, five hundred sixty-one million, six hundred five thousand, seven hundred five".