21164861155572 has 144 divisors (see below), whose sum is σ = 55935088831440. Its totient is φ = 6739257176064.

The previous prime is 21164861155531. The next prime is 21164861155573. The reversal of 21164861155572 is 27555116846112.

21164861155572 is a `hidden beast` number, since 2 + 1 + 1 + 6 + 4 + 8 + 6 + 11 + 55 + 572 = 666.

It can be written as a sum of positive squares in 8 ways, for example, as 9126223489296 + 12038637666276 = 3020964^2 + 3469674^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21164861155573) 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, 65549358 + ... + 65871450.

It is an arithmetic number, because the mean of its divisors is an integer number (388438116885).

Almost surely, 2^{21164861155572} 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 21164861155572, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27967544415720).

21164861155572 is an abundant number, since it is smaller than the sum of its proper divisors (34770227675868).

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

21164861155572 is a wasteful number, since it uses less digits than its factorization.

21164861155572 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322802 (or 322797 counting only the distinct ones).

The product of its digits is 4032000, while the sum is 54.

The spelling of 21164861155572 in words is "twenty-one trillion, one hundred sixty-four billion, eight hundred sixty-one million, one hundred fifty-five thousand, five hundred seventy-two".