19928686561 has 45 divisors (see below), whose sum is σ = 24162549201. Its totient is φ = 16435459656.

The previous prime is 19928686553. The next prime is 19928686573. The reversal of 19928686561 is 16568682991.

The square root of 19928686561 is 141169.

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

It is not a de Polignac number, because 19928686561 - 2³ = 19928686553 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 19928686561.

It is not an unprimeable number, because it can be changed into a prime (19928686961) by changing a digit.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 297443050 + ... + 297443116.

Almost surely, 2^19928686561 is an apocalyptic number.

19928686561 is the 141169-th square number.

19928686561 is the 70585-th centered octagonal number.

It is an amenable number.

19928686561 is a deficient number, since it is larger than the sum of its proper divisors (4233862640).

19928686561 is an frugal number, since it uses more digits than its factorization.

19928686561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 248 (or 117 counting only the distinct ones).

The product of its digits is 11197440, while the sum is 61.

The spelling of 19928686561 in words is "nineteen billion, nine hundred twenty-eight million, six hundred eighty-six thousand, five hundred sixty-one".