20851728569 has 6 divisors (see below), whose sum is σ = 24256092474. Its totient is φ = 17872910160.

The previous prime is 20851728551. The next prime is 20851728571. The reversal of 20851728569 is 96582715802.

It can be written as a sum of positive squares in only one way, i.e., 20574172969 + 277555600 = 143437^2 + 16660^2 .

It is a de Polignac number, because none of the positive numbers 2^k-20851728569 is a prime.

It is a super-2 number, since 2×20851728569² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 20851728569.

It is not an unprimeable number, because it can be changed into a prime (20851728269) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 212772692 + ... + 212772789.

It is an arithmetic number, because the mean of its divisors is an integer number (4042682079).

Almost surely, 2^20851728569 is an apocalyptic number.

It is an amenable number.

20851728569 is a deficient number, since it is larger than the sum of its proper divisors (3404363905).

20851728569 is an equidigital number, since it uses as much as digits as its factorization.

20851728569 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 425545495 (or 425545488 counting only the distinct ones).

The product of its (nonzero) digits is 2419200, while the sum is 53.

The spelling of 20851728569 in words is "twenty billion, eight hundred fifty-one million, seven hundred twenty-eight thousand, five hundred sixty-nine".