19665621056 has 42 divisors (see below), whose sum is σ = 40416133290. Its totient is φ = 9493722112.

The previous prime is 19665621011. The next prime is 19665621067. The reversal of 19665621056 is 65012656691.

It can be written as a sum of positive squares in 3 ways, for example, as 3526459456 + 16139161600 = 59384^2 + 127040^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 19665621056.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 128861 + ... + 236508.

Almost surely, 2^19665621056 is an apocalyptic number.

19665621056 is a gapful number since it is divisible by the number (16) formed by its first and last digit.

It is an amenable number.

19665621056 is an abundant number, since it is smaller than the sum of its proper divisors (20750512234).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

19665621056 is an equidigital number, since it uses as much as digits as its factorization.

19665621056 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 365439 (or 365400 counting only the distinct ones).

The product of its (nonzero) digits is 583200, while the sum is 47.

It can be divided in two parts, 196656 and 21056, that added together give a palindrome (217712).

The spelling of 19665621056 in words is "nineteen billion, six hundred sixty-five million, six hundred twenty-one thousand, fifty-six".