19811315664 has 320 divisors, whose sum is σ = 68084928000. Its totient is φ = 5463230976.

The previous prime is 19811315651. The next prime is 19811315683. The reversal of 19811315664 is 46651311891.

19811315664 is a `hidden beast` number, since 1 + 9 + 81 + 1 + 3 + 1 + 566 + 4 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 7101982 + ... + 7104770.

It is an arithmetic number, because the mean of its divisors is an integer number (212765400).

Almost surely, 2^19811315664 is an apocalyptic number.

19811315664 is a gapful number since it is divisible by the number (14) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 19811315664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34042464000).

19811315664 is an abundant number, since it is smaller than the sum of its proper divisors (48273612336).

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

19811315664 is an equidigital number, since it uses as much as digits as its factorization.

19811315664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2854 (or 2830 counting only the distinct ones).

The product of its digits is 155520, while the sum is 45.

The spelling of 19811315664 in words is "nineteen billion, eight hundred eleven million, three hundred fifteen thousand, six hundred sixty-four".