19681564681 has 9 divisors (see below), whose sum is σ = 20067502791. Its totient is φ = 19302919272.

The previous prime is 19681564657. The next prime is 19681564687. The reversal of 19681564681 is 18646518691.

The square root of 19681564681 is 140291.

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., 14188383225 + 5493181456 = 119115^2 + 74116^2 .

It is not a de Polignac number, because 19681564681 - 2⁹ = 19681564169 is a prime.

It is a super-2 number, since 2×19681564681² (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 (19681564687) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 7434100 + ... + 7436746.

Almost surely, 2^19681564681 is an apocalyptic number.

19681564681 is the 140291-st square number.

19681564681 is the 70146-th centered octagonal number.

It is an amenable number.

19681564681 is a deficient number, since it is larger than the sum of its proper divisors (385938110).

19681564681 is an frugal number, since it uses more digits than its factorization.

19681564681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5400 (or 2700 counting only the distinct ones).

The product of its digits is 2488320, while the sum is 55.

The spelling of 19681564681 in words is "nineteen billion, six hundred eighty-one million, five hundred sixty-four thousand, six hundred eighty-one".