19966534561 has 8 divisors (see below), whose sum is σ = 21350355624. Its totient is φ = 18605971200.

The previous prime is 19966534507. The next prime is 19966534573. The reversal of 19966534561 is 16543566991.

It can be written as a sum of positive squares in 4 ways, for example, as 11762703936 + 8203830625 = 108456^2 + 90575^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 19966534561 - 2⁷ = 19966534433 is a prime.

It is not an unprimeable number, because it can be changed into a prime (19966532561) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5812650 + ... + 5816083.

It is an arithmetic number, because the mean of its divisors is an integer number (2668794453).

Almost surely, 2^19966534561 is an apocalyptic number.

It is an amenable number.

19966534561 is a deficient number, since it is larger than the sum of its proper divisors (1383821063).

19966534561 is a wasteful number, since it uses less digits than its factorization.

19966534561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11628851.

The product of its digits is 5248800, while the sum is 55.

The spelling of 19966534561 in words is "nineteen billion, nine hundred sixty-six million, five hundred thirty-four thousand, five hundred sixty-one".