20561609727 has 16 divisors (see below), whose sum is σ = 30890684160. Its totient is φ = 13514671800.

The previous prime is 20561609711. The next prime is 20561609741. The reversal of 20561609727 is 72790616502.

20561609727 is a `hidden beast` number, since 2 + 0 + 5 + 616 + 0 + 9 + 7 + 27 = 666.

It is not a de Polignac number, because 20561609727 - 2⁴ = 20561609711 is a prime.

It is a super-2 number, since 2×20561609727² (a number of 21 digits) contains 22 as substring.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20561602727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5361049 + ... + 5364882.

It is an arithmetic number, because the mean of its divisors is an integer number (1930667760).

Almost surely, 2^20561609727 is an apocalyptic number.

20561609727 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

20561609727 is a deficient number, since it is larger than the sum of its proper divisors (10329074433).

20561609727 is a wasteful number, since it uses less digits than its factorization.

20561609727 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10726011 (or 10726005 counting only the distinct ones).

The product of its (nonzero) digits is 317520, while the sum is 45.

The spelling of 20561609727 in words is "twenty billion, five hundred sixty-one million, six hundred nine thousand, seven hundred twenty-seven".