19971613728 has 144 divisors (see below), whose sum is σ = 63632290176. Its totient is φ = 5888401920.

The previous prime is 19971613699. The next prime is 19971613733. The reversal of 19971613728 is 82731617991.

It is a happy number.

19971613728 is a `hidden beast` number, since 19 + 9 + 7 + 1 + 613 + 7 + 2 + 8 = 666.

It is a tau number, because it is divible by the number of its divisors (144).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 32025 + ... + 202407.

It is an arithmetic number, because the mean of its divisors is an integer number (441890904).

Almost surely, 2^19971613728 is an apocalyptic number.

19971613728 is a gapful number since it is divisible by the number (18) 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 19971613728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31816145088).

19971613728 is an abundant number, since it is smaller than the sum of its proper divisors (43660676448).

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

19971613728 is a wasteful number, since it uses less digits than its factorization.

19971613728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 170447 (or 170436 counting only the distinct ones).

The product of its digits is 1143072, while the sum is 54.

It can be divided in two parts, 199716 and 13728, that added together give a square (213444 = 462²).

The spelling of 19971613728 in words is "nineteen billion, nine hundred seventy-one million, six hundred thirteen thousand, seven hundred twenty-eight".