21781712518272 has 384 divisors, whose sum is σ = 71869049366400. Its totient is φ = 6202901053440.

The previous prime is 21781712518261. The next prime is 21781712518273. The reversal of 21781712518272 is 27281521718712.

It is a happy number.

21781712518272 is a `hidden beast` number, since 2 + 17 + 81 + 7 + 12 + 518 + 27 + 2 = 666.

21781712518272 is digitally balanced in base 5, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (384).

It is not an unprimeable number, because it can be changed into a prime (21781712518273) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 3474508354 + ... + 3474514622.

It is an arithmetic number, because the mean of its divisors is an integer number (187158982725).

Almost surely, 2^{21781712518272} is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21781712518272, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35934524683200).

21781712518272 is an abundant number, since it is smaller than the sum of its proper divisors (50087336848128).

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

21781712518272 is a wasteful number, since it uses less digits than its factorization.

21781712518272 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7644 (or 7629 counting only the distinct ones).

The product of its digits is 1756160, while the sum is 54.

The spelling of 21781712518272 in words is "twenty-one trillion, seven hundred eighty-one billion, seven hundred twelve million, five hundred eighteen thousand, two hundred seventy-two".