20985288769 has 9 divisors (see below), whose sum is σ = 21688711779. Its totient is φ = 20303998080.

The previous prime is 20985288719. The next prime is 20985288773. The reversal of 20985288769 is 96788258902.

The square root of 20985288769 is 144863.

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

It can be written as a sum of positive squares in only one way, i.e., 20114330625 + 870958144 = 141825^2 + 29512^2 .

It is not a de Polignac number, because 20985288769 - 2¹⁹ = 20984764481 is a prime.

It is a super-2 number, since 2×20985288769² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20985288769.

It is not an unprimeable number, because it can be changed into a prime (20985288719) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 4488417 + ... + 4493089.

Almost surely, 2^20985288769 is an apocalyptic number.

20985288769 is the 144863-rd square number.

20985288769 is the 72432-nd centered octagonal number.

It is an amenable number.

20985288769 is a deficient number, since it is larger than the sum of its proper divisors (703423010).

20985288769 is an frugal number, since it uses more digits than its factorization.

20985288769 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9408 (or 4704 counting only the distinct ones).

The product of its (nonzero) digits is 34836480, while the sum is 64.

Multiplying 20985288769 by its sum of digits (64), we get a square (1343058481216 = 1158904²).

The spelling of 20985288769 in words is "twenty billion, nine hundred eighty-five million, two hundred eighty-eight thousand, seven hundred sixty-nine".