20747809681 has 27 divisors (see below), whose sum is σ = 22751185779. Its totient is φ = 18916616448.

The previous prime is 20747809679. The next prime is 20747809703. The reversal of 20747809681 is 18690874702.

The square root of 20747809681 is 144041.

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

It can be written as a sum of positive squares in 13 ways, for example, as 4517049681 + 16230760000 = 67209^2 + 127400^2 .

It is not a de Polignac number, because 20747809681 - 2¹ = 20747809679 is a prime.

It is a super-2 number, since 2×20747809681² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20747809651) 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 26 ways as a sum of consecutive naturals, for example, 90601675 + ... + 90601903.

Almost surely, 2^20747809681 is an apocalyptic number.

20747809681 is the 144041-st square number.

20747809681 is the 72021-st centered octagonal number.

It is an amenable number.

20747809681 is a deficient number, since it is larger than the sum of its proper divisors (2003376098).

20747809681 is an frugal number, since it uses more digits than its factorization.

20747809681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 566 (or 283 counting only the distinct ones).

The product of its (nonzero) digits is 1354752, while the sum is 52.

The spelling of 20747809681 in words is "twenty billion, seven hundred forty-seven million, eight hundred nine thousand, six hundred eighty-one".